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4 Easy Steps to Check Ohms with a Multimeter

Electrical circuits are the backbone of modern society, powering everything from our smartphones to the lights in our homes. Understanding how to measure the resistance of a circuit is crucial for troubleshooting electrical problems and ensuring the safe operation of electrical devices. This guide will provide a comprehensive overview of how to check ohms with a multimeter, a versatile tool that allows you to measure voltage, current, and resistance. Whether you’re a novice electrician or a seasoned engineer, having a firm grasp of this technique is essential for any electrical work.

Before delving into the steps involved in checking ohms, it’s important to understand the concept of resistance. Resistance is a measure of how difficult it is for an electrical current to flow through a material. The higher the resistance, the more difficult it is for current to flow. Resistance is measured in ohms, and it is represented by the Greek letter Omega (Ω). The ohm is named after Georg Ohm, a German physicist who made significant contributions to the study of electricity.

To check ohms with a multimeter, you will need a multimeter, a device that combines multiple measuring functions into a single unit. Multimeters are available in both analog and digital formats, and either type can be used for this task. Once you have your multimeter, follow these steps: 1) Set the multimeter to the ohms function. This is typically indicated by the Omega (Ω) symbol. 2) Connect the multimeter’s probes to the circuit you want to measure. The red probe should be connected to the positive terminal, and the black probe should be connected to the negative terminal. 3) Read the display on the multimeter. The reading will be in ohms, and it will indicate the resistance of the circuit you are measuring.

Setting the Ohmmeter

Before using an ohmmeter to measure resistance, it’s crucial to set it up correctly. Follow these steps to ensure accurate readings:

Select the Correct Ohmmeter Scale: Choose an ohmmeter scale that corresponds to the expected resistance range of the circuit you’re testing. If you don’t know the approximate resistance, start with a higher scale and adjust it down as needed.
Zero the Ohmmeter: This step is essential to eliminate any errors caused by the ohmmeter’s internal resistance. To zero an ohmmeter:
- Connect the two test probes together.
- Rotate the "zero adjust" knob or push the "zero" button (if your ohmmeter has one) until the display reads zero ohms.
- Separate the probes and ensure the display remains at zero.
Meter Type Zeroing Method

Analog Ohmmeter Use the “zero adjust” knob to align the needle with the zero mark.

Digital Ohmmeter Push the “zero” button to reset the display to zero ohms.
Choose the Appropriate Test Leads: Use high-quality test leads with sharp, clean tips to ensure good electrical contact. Avoid using frayed or damaged leads, as they can introduce errors.
Connect the Ohmmeter to the Circuit: Connect the positive (red) probe to one terminal of the circuit being tested and the negative (black) probe to the other terminal. Ensure that the probes make firm contact with the terminals.

Meter Type	Zeroing Method
Analog Ohmmeter	Use the “zero adjust” knob to align the needle with the zero mark.
Digital Ohmmeter	Push the “zero” button to reset the display to zero ohms.

Connecting Test Leads

1. Identify the test leads: Multimeters typically have two test leads, a red one and a black one. The red lead is typically positive, while the black lead is negative.

2. Connect the test leads to the multimeter: Insert the red test lead into the port labeled “VΩmA” or “Ω” on the multimeter. Insert the black test lead into the port labeled “COM” or “0”.

3. Select the correct ohmmeter setting: Most multimeters have a rotary switch or a button that allows you to select the ohmmeter setting. The setting you choose will depend on the range of resistance you are measuring. If you are not sure what range to use, start with the highest setting and then decrease it until you get a stable reading.

Measurement Range	Ohmmeter Setting
0 – 200 ohms	Ω200
200 – 2,000 ohms	Ω2k
2,000 – 20,000 ohms	Ω20k
20,000 – 200,000 ohms	Ω200k
200,000 ohms – 2 Megaohms	Ω2M

Measuring Ohms on a Resistor

To measure the resistance of a resistor using a multimeter, follow these steps:

1. Connect the Multimeter to the Resistor

Connect the positive lead of the multimeter to one terminal of the resistor, and the negative lead of the multimeter to the other terminal.

2. Select the Ohms Function

On the multimeter, select the ohms function. This is typically represented by the symbol Ω. Some multimeters may have multiple ohms ranges, so select the range that is appropriate for the expected resistance of the resistor.

3. Read the Resistance

The multimeter will display the resistance in ohms. The reading may fluctuate slightly, so it is best to take an average of several readings.

4. Interpreting the Results

The measured resistance should be close to the expected resistance of the resistor. If the measured resistance is significantly different from the expected resistance, it could indicate a problem with the resistor or the multimeter. The following table summarizes the possible interpretations of the measured resistance:

Measured Resistance	Interpretation
Close to expected resistance	Resistor is within tolerance.
Significantly lower than expected resistance	Resistor may be shorted or damaged.
Significantly higher than expected resistance	Resistor may be open or damaged.

Troubleshooting Open Circuits

An open circuit is a break in the electrical connection, which prevents the flow of current. This can be caused by a variety of factors, such as a loose connection, a broken wire, or a damaged component. To troubleshoot an open circuit, you can use a multimeter to check the continuity of the circuit.

Checking Continuity

To check the continuity of a circuit, you need to set the multimeter to the ohms setting. Then, touch the probes of the multimeter to the two terminals of the circuit. If the circuit is complete, the multimeter will display a reading of zero ohms. If the circuit is open, the multimeter will display a reading of infinity ohms.

Identifying the Open Circuit

If the multimeter displays a reading of infinity ohms, it means that there is an open circuit somewhere in the circuit. To identify the location of the open circuit, you can use the following steps:

Disconnect the circuit from the power source.
Set the multimeter to the ohms setting.
Touch one probe of the multimeter to one terminal of the circuit.
Touch the other probe of the multimeter to different points along the circuit.
When the multimeter displays a reading of zero ohms, you have found the location of the open circuit.

Repairing the Open Circuit

Once you have identified the location of the open circuit, you can repair it by soldering the broken wire or replacing the damaged component. If you are not comfortable performing electrical repairs, you should contact a qualified electrician.

Additional Tips for Troubleshooting Open Circuits

Here are some additional tips for troubleshooting open circuits:

Check the power source to make sure that it is working properly.
Inspect the wires and connections for any signs of damage.
Use a flashlight to look for any breaks in the wires.
If you are testing a circuit that is powered by a battery, check the battery to make sure that it is not dead.

Symptom	Possible Cause
Multimeter displays a reading of infinity ohms	Open circuit
Multimeter displays a reading of zero ohms	Short circuit

Testing Continuity

Continuity testing is a crucial step when troubleshooting electrical circuits. It verifies the presence of a complete path for current flow between two points in a circuit.

Set the Multimeter to Ohms Mode: Rotate the dial to the ohms (Ω) symbol, which measures electrical resistance.
Touch the Probe Tips Together: With the multimeter powered on, gently touch the red and black probe tips together. A reading close to zero ohms should be displayed, indicating continuity.
Connect the Probes to the Test Points: Identify the two points in the circuit you want to test. Connect the red probe to one point and the black probe to the other.
Observe the Reading: If the multimeter displays a reading close to zero ohms, there is continuity between the test points. If the reading is high or infinity (∞), there is an open circuit.
Check for Short Circuits: If the multimeter displays a reading of zero ohms even when the probe tips are separated, this indicates a short circuit, where current is flowing through an unintended path.
Troubleshooting Tips:

Reading Possible Cause

Zero ohms Continuous circuit

High or infinity ohms Open circuit, broken wire

Zero ohms with probes separated Short circuit

Reading	Possible Cause
Zero ohms	Continuous circuit
High or infinity ohms	Open circuit, broken wire
Zero ohms with probes separated	Short circuit

Remember to be cautious when working with live circuits. Disconnect the power source before testing continuity to avoid accidents.

Interpreting Ohmmeter Readings

Understanding the readings from an ohmmeter is crucial for accurate circuit analysis and troubleshooting.

Continuity

If the ohmmeter reading is close to zero ohms (typically below 5 ohms), it indicates continuity. This means that there is a conductive path between the test points.

Resistance

If the ohmmeter reading is greater than zero but significantly less than infinity, it indicates that there is resistance in the circuit. The value displayed represents the resistance in ohms.

Open Circuit

If the ohmmeter reading is infinity (OL), it indicates that the circuit is open. There is no conductive path between the test points.

Short Circuit

If the ohmmeter reading is zero ohms (0.00 ohms), it indicates a short circuit. There is a conductive path between the test points that has very low resistance.

Example: Table of Ohmmeter Readings

Reading	Interpretation
0 ohms	Short circuit
10 ohms	Resistance
∞ ohms	Open circuit

Overload Protection

Most ohmmeters have an overload protection feature to prevent damage to the meter if it is used to measure resistance in a live circuit. If the voltage across the test points exceeds a specific threshold, the ohmmeter will typically display an “OL” (overload) reading.

Accuracy Considerations

The accuracy of ohmmeter readings can be affected by several factors, including the quality of the meter, the test leads, and the temperature of the circuit being tested. It is important to use a high-quality ohmmeter and to ensure that the test leads are in good condition for accurate results.

How To Check Ohms With Multimeter

Ohms are a unit of measurement for electrical resistance. They are named after the German physicist Georg Ohm, who first discovered the relationship between current, voltage, and resistance. A multimeter is a device that can be used to measure ohms, as well as other electrical properties such as voltage and current.

To check ohms with a multimeter, you will need to set the multimeter to the ohms range. This is typically done by turning the dial to the ohms symbol (Ω). Once the multimeter is set to the ohms range, you will need to connect the probes to the component you are testing. The black probe should be connected to the negative terminal of the component, and the red probe should be connected to the positive terminal.

Once the probes are connected, the multimeter will display the resistance of the component in ohms. If the component is a conductor, the resistance will be low. If the component is an insulator, the resistance will be high. If the multimeter displays an infinite resistance, it means that the component is open.

1. Calculate Amps on a Parallel Circuit: A Step-by-Step Guide

Calculating the amperage in parallel circuits is essential for proper electrical system design and maintenance. By understanding the fundamental principles of current distribution in parallel connections, you can accurately determine the total current flowing through each branch and the main circuit. This knowledge empowers you to ensure safe and efficient operation of your electrical systems.

In a parallel circuit, the current leaving the voltage source divides into multiple paths, each carrying a portion of the total current. The individual branch currents then recombine at the end of the circuit, flowing back to the voltage source. This unique configuration allows each branch to operate independently, with its current determined by the specific resistance and voltage present. However, the total current flowing through the main circuit is the sum of the individual branch currents, providing a crucial relationship between the parallel branches and the overall circuit.

To calculate the total amperage in a parallel circuit, you need to determine the individual branch currents and then sum them up. The branch current is calculated using Ohm’s law, which states that the current through a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor. By rearranging Ohm’s law, you can express the branch current as I = V/R, where I is the current in amps, V is the voltage in volts, and R is the resistance in ohms. By applying this equation to each branch of the parallel circuit, you can calculate the individual branch currents and then sum them up to obtain the total current flowing through the main circuit.

Understanding Parallel Circuits

In a parallel circuit, the electrical current flows through multiple paths, unlike in a series circuit where the current flows through a single path. This means that each device in a parallel circuit receives its own independent power source, and the total current flowing through the circuit is the sum of the currents flowing through each branch.

The following are some of the key characteristics of parallel circuits:

The voltage across each device in a parallel circuit is the same.
The total current flowing through a parallel circuit is the sum of the currents flowing through each branch.
If one device in a parallel circuit fails, the other devices will continue to operate.

Parallel circuits are often used in electrical systems because they provide several advantages over series circuits. For example, parallel circuits are more reliable because if one device fails, the other devices will continue to operate. Additionally, parallel circuits can be used to distribute power more evenly throughout a system.

Advantages of Parallel Circuits	Disadvantages of Parallel Circuits
More reliable	Can be more complex to design
Can be used to distribute power more evenly	Requires more wire

Calculating Total Current in Parallel Circuits

In a parallel circuit, the current is divided among the branches, and the total current is the sum of the currents in each branch. To calculate the total current in a parallel circuit, you need to know the current in each branch.

Measuring Current in Each Branch

To measure the current in each branch of a parallel circuit, you can use a multimeter. Set the multimeter to the current measurement mode, and then connect the probes to the ends of the branch. The multimeter will display the current in the branch.

Here is a table summarizing the steps for calculating total current in a parallel circuit:

Step	Description
1	Measure the current in each branch of the circuit.
2	Add up the currents in each branch to get the total current.

Determining Resistance in Parallel Circuits

When resistors are connected in parallel, the total resistance of the circuit is reduced compared to the resistance of any individual resistor. This is because current can flow through multiple paths in a parallel circuit, reducing the overall resistance. The formula for calculating the total resistance (Rt) of resistors in parallel is:

Rt = 1/(1/R1 + 1/R2 + … + 1/Rn)

Where R1, R2, …, Rn represent the resistances of the individual resistors in the parallel circuit.

For example, if you have three resistors with resistances of 10 ohms, 15 ohms, and 20 ohms connected in parallel, the total resistance of the circuit would be:

Rt = 1/(1/10 + 1/15 + 1/20)

Rt = 1/(0.1 + 0.0667 + 0.05)

Rt = 1/0.2167

Rt = 4.62 ohms

As you can see, the total resistance of the parallel circuit is less than the resistance of any individual resistor. This is because current can flow through multiple paths in the circuit, reducing the overall resistance.

The following table shows the relationship between the number of resistors in a parallel circuit and the total resistance:

Number of Resistors	Total Resistance
1	R1
2	R1 * R2 / (R1 + R2)
3	(R1 * R2 * R3) / (R1 * R2 + R2 * R3 + R3 * R1)
4	(R1 * R2 * R3 * R4) / (R1 * R2 * R3 + R1 * R2 * R4 + R1 * R3 * R4 + R2 * R3 * R4)
n	1/(1/R1 + 1/R2 + … + 1/Rn)

Using Ohm’s Law for Parallel Calculations

Ohm’s Law, a fundamental principle in electrical circuits, provides the relationship between voltage (V), current (I), and resistance (R): V = IR. In a parallel circuit, where multiple resistors are connected in parallel, the total current flowing through the circuit is the sum of the currents through each individual resistor.

To apply Ohm’s Law to parallel calculations, let’s consider a circuit with two resistors, R1 and R2, connected in parallel across a voltage source of V volts. The voltage across each resistor is the same, V, and the current through each resistor is given by:

I1 = V / R1

and

I2 = V / R2

The total current flowing through the circuit, denoted as I, is:

I = I1 + I2 = V / R1 + V / R2

Factorizing V from the equation, we get:

I = V(1/R1 + 1/R2)

The term in parentheses, (1/R1 + 1/R2), represents the total conductance of the circuit, denoted as G. Conductance is the inverse of resistance, and its unit is siemens (S). Substituting G into the equation, we get:

I = VG

This equation shows that the total current in a parallel circuit is directly proportional to the voltage and the total conductance of the circuit.

Applying Kirchhoff’s Current Law

Kirchhoff’s Current Law (KCL) states that the total current entering a junction must equal the total current leaving the junction. In other words, the current flowing into a node must equal the current flowing out of the node.

This law can be used to calculate the current flowing through any branch of a parallel circuit. To do this, first identify the node at which the branch is connected. Then, apply KCL to the node. The current flowing into the node must be equal to the current flowing out of the node, including the current flowing through the branch.

For example, consider the following parallel circuit:

Figure: Parallel circuit

The current flowing into node A is equal to the current flowing out of node A. Therefore,

“`
I_1 + I_2 + I_3 = I_4
“`

where:

* I_1 is the current flowing through resistor R_1
* I_2 is the current flowing through resistor R_2
* I_3 is the current flowing through resistor R_3
* I_4 is the current flowing through resistor R_4

We can use this equation to calculate the current flowing through any branch of the circuit. For example, to calculate the current flowing through resistor R_1, we can rearrange the equation as follows:

“`
I_1 = I_4 – I_2 – I_3
“`

Once we know the current flowing through each branch of the circuit, we can use Ohm’s Law to calculate the voltage across each branch.

Calculating Amps in a Parallel Circuit

In a parallel circuit, the current (amps) flowing through each branch is inversely proportional to the resistance of that branch. The total current (amps) flowing through the entire circuit is the sum of the currents flowing through each branch.

Practical Applications of Parallel Circuit Calculations

Calculating Power Consumption

Parallel circuit calculations can help you determine the power consumption of individual devices in a circuit. By knowing the current and voltage of each branch, you can calculate the power consumed by each device using the formula: Power = Voltage x Current.

Designing Electrical Systems

When designing electrical systems, it’s crucial to ensure that the circuits can handle the expected current load. Parallel circuit calculations help determine the appropriate wire gauges, breakers, and other components to prevent overheating and electrical fires.

Troubleshooting Electrical Circuits

Identifying problems in electrical circuits often involves parallel circuit calculations. By measuring the current in each branch, you can identify potential issues such as short circuits or open circuits.

Understanding Electrical Safety

Parallel circuit calculations are essential for understanding electrical safety. By knowing how current flows in a circuit, you can make informed decisions about how to use and handle electrical equipment safely.

Example: Calculating Amps in a Parallel Circuit

Consider a parallel circuit with three branches. The resistances of the branches are 10 ohms, 15 ohms, and 20 ohms, respectively. The voltage across the circuit is 12 volts. Calculate the current flowing through each branch and the total current flowing through the circuit.

Branch 1 Current: 12 volts / 10 ohms = 1.2 amps

Branch 2 Current: 12 volts / 15 ohms = 0.8 amps

Branch 3 Current: 12 volts / 20 ohms = 0.6 amps

Total Current: 1.2 amps + 0.8 amps + 0.6 amps = 2.6 amps

Branch	Resistance (ohms)	Current (amps)
1	10	1.2
2	15	0.8
3	20	0.6
Total		2.6

Parallel Circuit Current Calculation

In a parallel circuit, the total current is the sum of the currents flowing through each branch. Use the following steps to calculate the amps on a parallel circuit:

Find the total resistance of the circuit using the formula: 1/Total Resistance = 1/Resistance1 + 1/Resistance2 + 1/Resistance3 + …

Calculate the voltage drop across each branch using Ohm’s Law: Voltage = Current * Resistance

Use Ohm’s Law to calculate the current flowing through each branch: Current = Voltage / Resistance

Add up the currents flowing through each branch to find the total current in the circuit.

Real-World Examples of Parallel Circuits

Parallel circuits have numerous applications in everyday life. Here are a few practical examples:

Household Electrical Systems

Most household electrical systems are wired in parallel, allowing multiple appliances and devices to operate simultaneously without affecting the overall circuit performance. This enables users to plug in and use various appliances (e.g., lights, TVs, refrigerators) without worrying about overloading the circuit.

Automotive Electrical Systems

Automotive electrical systems also employ parallel circuits. For instance, the headlights, taillights, and other electrical components are connected in parallel, ensuring that each component receives the necessary voltage and that the failure of one component does not affect the operation of the others.

Industrial Machinery

In industrial settings, parallel circuits are used to control and power various machines. For example, in a conveyor system, multiple motors may be connected in parallel to provide the necessary power to move the conveyor belt. This configuration allows for individual motor repairs or replacements without shutting down the entire system.

Troubleshooting Parallel Circuits

1. Check for Loose Connections

Any loose connections within the circuit can lead to electrical problems, including insufficient current flow and overheating.

2. Inspect Wiring

Ensure that all wiring is correctly connected and properly insulated to prevent shorts and reduce resistance.

3. Test Components

Use a multimeter to test the continuity of circuit components, such as resistors and capacitors.

4. Check Voltage

Verify that the voltage source provides the correct voltage for the circuit to function properly.

5. Measure Current

Use a clamp meter or multimeter to check the current flowing through each branch of the circuit.

6. Remove and Isolate Faulty Components

If a component is identified as faulty, disconnect it from the circuit to prevent further damage or safety hazards.

7. Reconnect Components

Once the faulty components have been replaced or repaired, reconnect them to the circuit and test the system to ensure proper operation.

8. Check Branch Currents and Calculate Total Current

In a parallel circuit, the total current is the sum of the currents flowing through each branch. To troubleshoot, calculate the total current based on the branch currents:

Total Current (I_total)

I₁ + I₂ + … + I_n

If the calculated total current does not match the measured total current, there may be a fault in the circuit.

Safety Considerations for Parallel Circuits

When working with parallel circuits, safety is essential. Here are some important considerations to keep in mind:

1. Use Proper Insulation

All wires and connections in a parallel circuit should be properly insulated to prevent electrical shocks or fires.

2. Avoid Overloading

Do not overload a parallel circuit with too many devices. This can cause the circuit to overheat and pose a fire hazard.

3. Use Fuses or Circuit Breakers

Install fuses or circuit breakers in the circuit to protect it from overloads and short circuits.

4. Ground the Circuit

Properly ground the circuit to provide a safe path for electrical current in case of a fault.

5. Keep Children Away

Keep children away from parallel circuits and electrical equipment to prevent accidents.

6. Use Proper Tools

Always use insulated tools when working on a parallel circuit.

7. Avoid Contact with Live Wires

Never touch live wires or terminals with your bare hands.

8. Disconnect the Circuit Before Working on It

Always disconnect the power to the circuit before performing any maintenance or repairs.

9. Be Aware of the Dangers of Electricity

Electricity can be dangerous, so always exercise caution and consult with a qualified electrician if you are not familiar with electrical work.

Safety Consideration	Potential Hazard	Preventive Measure
Lack of insulation	Electrical shock, fire	Use proper insulation
Overloading	Fire hazard	Avoid overloading
Absence of fuses or circuit breakers	Overloads, short circuits	Install fuses or circuit breakers

Advanced Techniques for Parallel Circuit Analysis

1. Using Ohm’s Law for Parallel Circuits

In a parallel circuit, the current flowing through each branch is inversely proportional to the resistance of that branch. This means that the branch with the lowest resistance will carry the most current.

2. Using Kirchhoff’s Current Law

Kirchhoff’s current law states that the sum of the currents entering a junction is equal to the sum of the currents leaving the junction. This law can be used to find the total current flowing through a parallel circuit.

3. Using the Voltage Divider Rule

The voltage divider rule states that the voltage across each branch of a parallel circuit is equal to the voltage across the entire circuit. This rule can be used to find the voltage across any branch of a parallel circuit.

4. Using the Power Divider Rule

The power divider rule states that the power dissipated by each branch of a parallel circuit is equal to the power dissipated by the entire circuit multiplied by the fraction of the total resistance that is in that branch.

5. Using Superposition

Superposition is a technique that can be used to analyze complex circuits by breaking them down into simpler circuits. This technique can be used to find the current, voltage, or power in any branch of a parallel circuit.

6. Using Matrix Methods

Matrix methods can be used to analyze complex circuits that contain multiple parallel branches. This technique is more complex than the other techniques, but it can be used to find the current, voltage, or power in any branch of a parallel circuit.

7. Using Computer Simulation

Computer simulation can be used to analyze complex circuits that contain multiple parallel branches. This technique is the most complex of the techniques listed here, but it can be used to find the current, voltage, or power in any branch of a parallel circuit.

8. Identifying Parallel Circuits in Electrical Systems

Parallel circuits are common in electrical systems. They are used to distribute power to multiple devices and to provide redundant pathways for current flow. Parallel circuits can be identified by their characteristic branching structure.

9. Troubleshooting Parallel Circuits

Parallel circuits can be difficult to troubleshoot because there are multiple pathways for current flow. However, there are a few general troubleshooting techniques that can be used to identify and fix problems in parallel circuits.

10. Advanced Techniques for Parallel Circuit Analysis – Thevenin’s and Norton’s Theorems

Thevenin’s theorem and Norton’s theorem are two advanced techniques that can be used to analyze parallel circuits. These techniques can be used to simplify complex circuits and to find the current, voltage, or power in any branch of a parallel circuit. Thevenin’s theorem is used to replace a complex circuit with a single voltage source and a single resistor. Norton’s theorem is used to replace a complex circuit with a single current source and a single resistor.

Technique	Advantages	Disadvantages
Ohm’s Law	Simple to use	Only works for linear circuits
Kirchhoff’s Current Law	Can be used to analyze any circuit	Can be difficult to apply to complex circuits
Voltage Divider Rule	Simple to use	Only works for circuits with a single voltage source
Power Divider Rule	Simple to use	Only works for circuits with a single power source
Superposition	Can be used to analyze complex circuits	Can be difficult to apply to complex circuits
Matrix Methods	Can be used to analyze complex circuits	Complex to apply
Computer Simulation	Can be used to analyze complex circuits	Requires specialized software

How To Calculate Amps On A Paralllel Circuit

In a parallel circuit, the current is divided among the branches of the circuit. The total current is the sum of the currents in each branch. To calculate the current in each branch, we use Ohm’s law: I = V/R, where I is the current in amps, V is the voltage in volts, and R is the resistance in ohms.

For example, consider a parallel circuit with three branches. The voltage across each branch is 12 volts. The resistances of the branches are 2 ohms, 4 ohms, and 6 ohms, respectively. To calculate the current in each branch, we use Ohm’s law:

I1 = V/R1 = 12 volts / 2 ohms = 6 amps
I2 = V/R2 = 12 volts / 4 ohms = 3 amps
I3 = V/R3 = 12 volts / 6 ohms = 2 amps

The total current in the circuit is the sum of the currents in each branch: I = I1 + I2 + I3 = 6 amps + 3 amps + 2 amps = 11 amps.

3 Easy Steps to Measure Electric Current Using a Multimeter

Measuring electric current accurately is a crucial aspect of electrical troubleshooting and maintenance. Whether you’re a seasoned electrician or a DIY enthusiast, understanding how to measure electric current using a multimeter is essential. This comprehensive guide will provide you with step-by-step instructions and practical tips to help you obtain accurate current readings safely and efficiently.

To begin, you’ll need a reliable multimeter, a versatile tool that can measure various electrical parameters including current. Before using the multimeter, it’s important to set the dial to the appropriate current range. The range you choose should be higher than the expected current you intend to measure, to avoid damaging the meter. Once the multimeter is configured, connect the test leads to the circuit in series, ensuring that the current flows through the meter.

Selecting the Correct Multimeter

When measuring electric current, selecting the appropriate multimeter is essential to ensure accurate and reliable readings. The following considerations should guide your choice:

1. Range and Resolution

Determine the expected range of current you will be measuring and choose a multimeter with a range that encompasses it. For general-purpose applications, a multimeter with a range of at least 10 mA to 10 A is a good starting point. Higher ranges are available for measuring high currents in applications such as automotive or industrial settings.

Resolution, expressed in milliamps, microamps, or nanoamps, represents the smallest increment of change the multimeter can detect. A higher resolution provides finer precision in measurements, allowing you to differentiate between small changes in current.

**Table: Multimeter Ranges and Resolutions**

Range	Resolution
10 mA	1 mA
100 mA	10 mA
1 A	100 mA
10 A	1 A

2. Accuracy

Accuracy is expressed as a percentage of the reading +/- a fixed number of digits. For example, a multimeter with an accuracy of ±2% would indicate that the measurement is within 2% of the actual current value, plus or minus a small inherent error.

3. Features

Consider any additional features that may enhance your measurements, such as:

Auto-ranging: simplifies the selection of the appropriate measurement range

Backlit display: allows for visibility in low-light conditions

Data logging: records and stores measurements for later analysis

Understanding Multimeter Display Types

Multimeters come with various display types, each offering unique benefits and limitations. Understanding the different display options will help you choose the most suitable multimeter for your specific needs. Here are the three common multimeter display types:

Analog Display:

Analog multimeters use a needle that moves along a calibrated scale to indicate the measured value. They are relatively simple to use but can be less accurate than digital displays, especially in low-light conditions. Additionally, analog displays may have limited resolution, making it difficult to read precise measurements.

Digital Display:

Digital multimeters display the measured value on a digital panel, providing high accuracy and easy readability. They often feature additional functions such as data hold, auto-ranging, and backlight for enhanced user experience. Digital displays are also more versatile, allowing for measurements beyond simple voltage, current, and resistance.

Bar Graph Display:

Bar graph displays use a series of LEDs to indicate the measured value through a varying bar length. They provide a visual representation of the measurement but may lack the precision of numerical displays. Bar graph displays are commonly found in automotive testing and troubleshooting applications due to their ease of interpretation.

The table below summarizes the key differences between the three display types:

Display Type	Accuracy	Readability	Versatility
Analog	Lower	Moderate	Limited
Digital	Higher	Excellent	High
Bar Graph	Moderate	Good	Moderate

Setting the Multimeter to Ampere Mode

To measure electric current using a multimeter, it is essential to set the device to the ampere mode. Follow these steps to do so:

Locate the rotary dial on the multimeter, which typically has various settings for different measurement modes.

Find the ampere symbol (A) on the dial and rotate it to the corresponding position. For AC current, select the symbol with a tilde (~) above it, while for DC current, choose the symbol without the tilde.

Choose the appropriate current range for the measurement. Multimeters typically have multiple ranges, such as 200mA, 2A, and 10A. If you are unsure of the current value, start with the highest range and gradually decrease it until you get a stable reading.

Connect the multimeter leads to the circuit where you want to measure the current. The red lead should be connected to the positive terminal, and the black lead to the negative terminal.

Read the current value displayed on the multimeter screen. Ensure that the unit of measurement is amps (A).

Multimeter Settings for Measuring Electric Current
Measurement Type	Rotary Dial Setting	Lead Connection
DC Current	A without tilde (~)	Red lead to positive terminal, black lead to negative terminal
AC Current	A with tilde (~)	Red lead to positive terminal, black lead to negative terminal

Reading the Current Value

Once connected, you can read the current value displayed on the multimeter’s screen. Here are some tips for accurate readings:

1. Stable Connection:

Make sure both test leads have a secure connection to the circuit and multimeter terminals.

2. Correct Range:

Select an appropriate current range on the multimeter that exceeds the expected current value. If unsure, start with the highest range and gradually decrease it until you get a clear reading.

3. Lead Position:

Connect the test leads in series with the load (consumer) where you want to measure the current. The black (negative) lead should be connected before the load, and the red (positive) lead after the load.

4. Polarity:

For DC circuits, ensure the test leads are connected correctly to the circuit’s polarity. Red to positive (+) and black to negative (-).

5. Connect in Series:

To measure current, the multimeter must be connected in series with the circuit, effectively becoming part of the current path. The test leads should be connected as shown below:

Circuit Diagram	Multimeter Connection

By following these steps, you can ensure accurate and reliable current measurements using a multimeter.

Calibrating the Multimeter Regularly

Calibrating your multimeter regularly is essential to ensure its accuracy and reliability. Fortunately, the calibration process is relatively straightforward and can be performed using a few simple steps:

Gather Your Materials: You will need a stable voltage source (such as a battery or power supply) and a known resistor (with a value between 100 ohms and 1 kohm).
Set Up the Multimeter: Connect the multimeter in series with the voltage source and resistor. Set the multimeter to the DC voltage range that corresponds to the voltage of the source.
Measure the Voltage: Connect the multimeter probes to the terminals of the voltage source and measure the voltage. Record the measured voltage.
Calculate the Current: Using Ohm’s law (I = V/R), calculate the current flowing through the circuit using the measured voltage and the known resistance of the resistor.
Compare the Calculated Current: Compare the calculated current with the current indicated by the multimeter. If the two values are within a reasonable tolerance (typically within 1-2%), then the multimeter is calibrated correctly.
Adjust the Zero Point: If the multimeter does not indicate zero current when the probes are shorted together, adjust the zero point using the calibration knob or screw on the multimeter.
Repeat the Process: Repeat steps 3-6 for a range of voltage and resistance values to ensure accurate calibration across different ranges.
Record Calibration Data: After calibration, record the calibration data in the multimeter’s memory or a logbook for future reference.

Calibration Interval	Frequency
High-Precision Measurements	Every 6-12 months
General-Purpose Measurements	Every 1-2 years
Field or Infrequent Use	Every 3-5 years

Safety Precautions When Measuring Current

1. Choose the Right Meter

Select a multimeter capable of measuring the anticipated current level and type (AC or DC).

2. Set the Meter Correctly

Configure the multimeter to the appropriate current measurement setting before connecting to the circuit.

3. Use Proper Probes

Employ insulated test probes with sharp tips for reliable contact and minimize the risk of shock.

4. Connect Safely

Attach the red probe to the positive terminal of the circuit and the black probe to the negative terminal. Ensure secure connections.

5. Avoid Contact with Live Circuits

Never touch bare wires or components while measuring current.

6. Be Aware of Short Circuits

Connect the probes to the circuit in parallel to prevent short circuits.

7. Wear Protective Gear

Wear safety glasses and gloves when working with electrical circuits.

8. Test the Meter

Before measuring current, connect the probes together to verify that the meter is functioning correctly.

9. Check for Voltage First

Before measuring current, test for voltage in the circuit using the multimeter’s voltage measurement function to avoid potential hazards.

Current Range	Probe Type	Safety Precautions
Low (0-10 mA)	Thin, insulated probes	Handle with care to avoid damage
Medium (10-100 mA)	Medium-sized, insulated probes	Use caution and secure connections
High (over 100 mA)	Thick, high-current probes	Wear protective gear and avoid contact with bare conductors

General Tips

Before using a multimeter to measure electric current, it is important to take a few general precautions. Make sure that the multimeter is in good working condition and that the leads are properly connected. It is also important to select the correct range on the multimeter for the current you are expecting to measure. If the range is set too low, the multimeter may not be able to measure the current accurately. If the range is set too high, the multimeter may be damaged.

Specific Common Errors

1. Incorrect Connection of Leads

One of the most common errors when measuring electric current is connecting the leads incorrectly. The black lead should be connected to the common terminal on the multimeter, and the red lead should be connected to the current terminal. If the leads are connected incorrectly, the multimeter will not be able to measure the current accurately.

2. Incorrect Range Setting

Another common error is selecting the incorrect range on the multimeter. If the range is set too low, the multimeter may not be able to measure the current accurately. If the range is set too high, the multimeter may be damaged.

3. Broken or Damaged Leads

If the leads are broken or damaged, the multimeter will not be able to measure the current accurately. Inspect the leads for any damage before using the multimeter.

4. Incorrect Probe Placement

When measuring electric current, it is important to place the probes in the correct location. The probes should be placed in series with the circuit, meaning that the current must flow through the probes in order to reach the other component in the circuit.

5. Measuring AC Current with a DC Multimeter

A DC multimeter cannot be used to measure AC current. If you are trying to measure AC current, you will need to use an AC multimeter.

6. Measuring Current in a Live Circuit

It is dangerous to measure current in a live circuit. If you are not sure whether the circuit is live, do not attempt to measure the current.

7. Not Discharging Capacitors Before Measuring Current

If there are any capacitors in the circuit, they must be discharged before measuring the current. Capacitors can store a charge that can be dangerous if it is not discharged before working on the circuit.

8. Not Observing Safety Precautions

It is important to observe all safety precautions when working with electricity. This includes wearing proper safety gear and following all applicable electrical codes.

9. Using a Multimeter That Is Not Suitable for the Current Measurement

Not all multimeters are suitable for measuring electric current. Some multimeters are only designed to measure voltage or resistance. If you are unsure whether your multimeter is suitable for measuring current, consult the manufacturer’s instructions.

10. Ignoring the Effects of Temperature

The accuracy of a multimeter can be affected by temperature. If the multimeter is used in a cold environment, the readings may be lower than the actual current. If the multimeter is used in a hot environment, the readings may be higher than the actual current.

How to Measure Electric Current Using a Multimeter

Measuring electric current is a fundamental task for electricians and electronic enthusiasts. A multimeter is a versatile tool that can be used to measure various electrical properties, including current. Here’s a step-by-step guide on how to measure electric current using a multimeter:

Set the Meter to Current Measurement Mode: Identify the “A” or “mA” symbol on the multimeter’s dial. Rotate the dial to select the appropriate range for the expected current value.
Connect the Multimeter to the Circuit: Use the black (common) probe of the multimeter to connect to the negative terminal or ground point of the circuit. Connect the red (positive) probe to the point in the circuit where you want to measure the current.
Take the Measurement: The multimeter will display the electric current flowing through the circuit. The measurement will be in amperes (A) or milliamperes (mA), depending on the range you selected.
Record and Analyze Results: Note down the current measurement and compare it to the expected or known value. If the current is significantly different, further investigation may be necessary.

4 Simple Steps to Find Total Resistance in a Circuit

Unveiling the intricacies of electrical circuits, we embark on a journey to unravel the enigma of total resistance. Whether you’re a seasoned electrician or an aspiring enthusiast, understanding this fundamental concept is paramount to mastering the art of circuit design. In the realm of electricity, resistance reigns supreme as the governing force that impedes the flow of current, akin to a gatekeeper guarding the passage of electrons. By delving into the nuances of total resistance, we gain the power to predict and control the behavior of electrical circuits, paving the way for countless technological marvels.

Total resistance, the sum of individual resistances encountered along a circuit’s path, plays a pivotal role in shaping circuit behavior. It acts as a regulating force, determining the amount of current that can traverse the circuit. Imagine a circuit as a river, where total resistance governs the flow of water just as resistance controls the movement of electrons. By manipulating total resistance, we can regulate the flow of current, akin to adjusting the water flow in a river by altering the width or depth of its channel. Furthermore, total resistance influences voltage distribution, dictating the voltage available to each component within the circuit. Understanding the interplay between total resistance and these circuit parameters empowers us to design circuits that meet specific requirements and fulfill intended functions.

To unravel the mysteries of total resistance, we must venture into the realm of circuit analysis. The beauty of this endeavor lies in its simplicity, requiring only Ohm’s law, a fundamental principle that governs the relationship between voltage, current, and resistance. By applying Ohm’s law, we can calculate the total resistance of a circuit, providing a quantitative measure of its resistance to current flow. Moreover, total resistance can be affected by factors such as the physical properties of the conductors used, their length, and cross-sectional area. Delving into these factors unveils the intricate tapestry of circuit behavior, allowing us to tailor circuits for specific applications.

Understanding Resistance in Circuits

Resistance is a fundamental concept in electrical circuits. It is a measure of the opposition to the flow of electric current through a component or device. The higher the resistance, the more difficult it is for current to flow. Resistance is measured in ohms (Ω).

There are several factors that affect the resistance of a component:

Factor	Effect on Resistance
Material	Different materials have different resistivities, which is a measure of how easily they allow current to flow.
Length	The longer a component, the higher its resistance.
Cross-sectional area	The larger the cross-sectional area of a component, the lower its resistance.
Temperature	The resistance of most materials increases with temperature.

Understanding resistance is essential for analyzing and designing electrical circuits. It allows engineers to predict how much current will flow through a circuit and to design circuits that meet specific requirements.

Ohm’s Law and Resistance

Ohm’s law is a fundamental law in electrical engineering that relates the voltage (V) across a conductor to the current (I) flowing through it. The relationship is expressed as V = IR, where R is the resistance of the conductor.

Resistance is a measure of how difficult it is for current to flow through a conductor. It is measured in ohms (Ω). The higher the resistance, the more difficult it is for current to flow.

Types of Resistors

Resistors can be classified into two types: linear and nonlinear.

Linear resistors have a constant resistance over a wide range of voltages and currents. This means that the relationship between voltage and current is linear.
Nonlinear resistors have a resistance that varies with voltage or current. This means that the relationship between voltage and current is not linear.

Resistor Type	Description	Symbol
Fixed resistor	A resistor with a constant resistance	•
Variable resistor	A resistor whose resistance can be varied	• • •
Thermistor	A resistor whose resistance changes with temperature	• • •
LDR	A resistor whose resistance changes with light intensity	• • •

Types of Resistors in Circuits

Resistors are classified into various types based on their construction and characteristics. Here are some common types of resistors used in electrical circuits:

Fixed Resistors

Fixed resistors have a constant resistance value and are most commonly used in circuit applications. They are available in different resistance values and power ratings. Some examples of fixed resistors include:

Carbon resistors: Made of carbon particles, these resistors are inexpensive and commonly used in low-power applications.
Ceramic resistors: Known for their high stability and accuracy, they are used in precision applications.
Metal film resistors: Constructed from a thin metal film deposited on a ceramic core, they provide high precision and low noise.
Wirewound resistors: Composed of resistance wire wound around a core, these resistors can handle high power dissipation but have lower precision.

Variable Resistors

Variable resistors allow for the adjustment of resistance value within a specific range. They are commonly used as potentiometers (voltage dividers) or rheostats (current controllers). Some types of variable resistors include:

Potentiometers: These three-terminal resistors have a sliding or rotating contact that varies the resistance between its ends.
Rheostats: Similar to potentiometers, but they have only two terminals and are primarily used for controlling current.
Trimmer resistors: Small, adjustable resistors used for fine-tuning circuit parameters.

Special Purpose Resistors

Special purpose resistors are designed for specific applications, such as:

Fusable resistors: Designed to open the circuit when the current exceeds a certain level, acting as a safety measure.
Thermistors: Resistors whose resistance changes with temperature, used in temperature-sensing applications.
Varistors: Nonlinear resistors that act as voltage-dependent resistors, used in surge protection.

Series Circuits and Total Resistance

A series circuit is a circuit in which the components are connected in a single loop. The current flows through each component in turn, and the total resistance of the circuit is the sum of the resistances of the individual components.

Calculating Total Resistance in a Series Circuit

The total resistance of a series circuit can be calculated using the following formula:

“`
Total Resistance (RT) = Sum of Resistances (R1 + R2 + … + Rn)
“`

where:

* RT is the total resistance of the circuit
* R1, R2, …, Rn are the resistances of the individual components

Example

Consider a series circuit with three resistors: R1 = 10 ohms, R2 = 20 ohms, and R3 = 30 ohms. The total resistance of the circuit would be:

“`
RT = R1 + R2 + R3 = 10 ohms + 20 ohms + 30 ohms = 60 ohms
“`

Table of Resistances

The following table summarizes the resistances of the individual components and the total resistance of the series circuit:

Component	Resistance
R1	10 ohms
R2	20 ohms
R3	30 ohms
Total (RT)	60 ohms

Parallel Circuits and Total Resistance

A parallel circuit is one in which the components are connected across the voltage source, rather than in series. This means that the current has multiple paths to flow through, and the total resistance of the circuit is reduced.

The total resistance of a parallel circuit is given by the following formula:

$$1/R_{total} = 1/R_1 + 1/R_2 + … + 1/R_n$$

where

$R_{total}$ is the total resistance of the circuit
$R_1, R_2, …, R_n$ are the resistances of the individual components

For example, if you have two resistors in parallel, with resistances of 10 ohms and 15 ohms, the total resistance of the circuit would be:

$$1/R_{total} = 1/10 + 1/15$$

$$R_{total} = 6 ohms$$

As you can see, the total resistance of a parallel circuit is always less than the resistance of any of the individual components. This is because the current has multiple paths to flow through, so it is less likely to encounter resistance.

Calculating Total Resistance

To calculate the total resistance of a parallel circuit, you can use the following steps:

Find the reciprocal of the resistance of each component.
Add the reciprocals of the resistances together.
Take the reciprocal of the sum to find the total resistance.

For example, if you have three resistors in parallel, with resistances of 10 ohms, 15 ohms, and 20 ohms, the total resistance of the circuit would be:

Resistance (ohms)	Reciprocal (1/ohms)
10	0.1
15	0.0667
20	0.05
Total	0.2167

$$1/R_{total} = 0.2167$$

$$R_{total} = 4.62 ohms$$

Kirchhoff’s Voltage Law (KVL)

Kirchhoff’s Voltage Law (KVL) states that the algebraic sum of the voltages around a closed loop in a circuit is zero. In other words, the sum of the voltage rises must equal the sum of the voltage drops. This law is based on the conservation of energy, as voltage is a measure of potential energy per unit charge.

Applying KVL to a Simple Circuit

To apply KVL to a simple circuit, we can start at any point in the circuit and follow the path around the loop, adding up the voltages as we go. For example, consider the following circuit:

Component	Voltage
Battery	12 V
Resistor 1	-6 V
Resistor 2	-4 V
Resistor 3	-2 V

Starting at the positive terminal of the battery, we follow the path around the loop, adding up the voltages as we go: 12 V – 6 V – 4 V – 2 V = 0 V. This confirms KVL, as the sum of the voltages around the loop is zero.

Using KVL to Determine Unknown Voltages

KVL can also be used to determine unknown voltages in a circuit. For example, if we know the voltage across two resistors in a series circuit, we can use KVL to find the voltage across the third resistor. Similarly, if we know the voltage across a resistor and the current flowing through it, we can use KVL to find the voltage across the power source.

KVL and Series Circuits

In a series circuit, the current flowing through each component is the same. This means that the voltage drops across each resistor are proportional to the resistance of the resistor. KVL can be used to confirm this relationship, as the sum of the voltage drops across the resistors will equal the voltage of the power source.

KVL and Parallel Circuits

In a parallel circuit, the voltage across each component is the same. This means that the current flowing through each resistor is inversely proportional to the resistance of the resistor. KVL can be used to confirm this relationship, as the sum of the currents flowing through the resistors will equal the current from the power source.

Wheatstone Bridge Circuit

A Wheatstone bridge circuit is a type of electrical circuit used to measure an unknown resistance. It consists of four resistors arranged in a diamond shape, with a galvanometer connected between two of the vertices. A battery is connected across the other two vertices. When the bridge is balanced, the current through the galvanometer is zero, and the unknown resistance can be calculated from the values of the other resistors.

How to Use a Wheatstone Bridge

To use a Wheatstone bridge, follow these steps:

Connect the unknown resistance to one of the terminals of the bridge.
Connect a known resistance to the opposite terminal.
Connect a battery to the remaining two terminals.
Adjust the variable resistor until the galvanometer reads zero.
Calculate the unknown resistance using the following formula:
“`
Rx = R1 * R2 / R3
“`

Where:
- Rx is the unknown resistance
- R1 is the known resistance
- R2 is the variable resistor
- R3 is the fourth resistor in the bridge
Applications of Wheatstone Bridges

Wheatstone bridges are used in a variety of applications, including:
- Measuring the resistance of electrical components
- Calibrating other measuring instruments
- Detecting faults in electrical circuits
Advantages of Wheatstone Bridges

Wheatstone bridges offer a number of advantages over other methods of measuring resistance, including:
- High accuracy
- Wide range of measurement
- Simple to use
Disadvantages of Wheatstone Bridges

Wheatstone bridges also have some disadvantages, including:
- Can be sensitive to temperature changes
- Requires a skilled operator to obtain accurate results
Practical Applications of Total Resistance Calculations

Calculating the total resistance in a circuit is crucial for designing and analyzing electrical systems. Here are some practical applications:

Current Limiting

Total resistance limits the current flow in a circuit. By calculating the total resistance, engineers can ensure that the current does not exceed the safe operating limits of components.

Voltage Division

In a series circuit, the total resistance determines the voltage drop across each resistor. By calculating the total resistance, engineers can design circuits to distribute voltage appropriately.

Power Consumption

Total resistance affects the power consumption of a circuit. By calculating the total resistance, engineers can determine the power dissipated in each component and optimize the circuit’s efficiency.

Circuit Analysis and Troubleshooting

Total resistance calculations help in troubleshooting electrical circuits. By measuring the total resistance and comparing it to the expected value, technicians can identify faulty components or design errors.

Fuse Selection

Fuses are safety devices that protect circuits from excessive current. When choosing a fuse, engineers must consider the total resistance of the circuit to ensure that the fuse will blow before the circuit is damaged.

Battery Life Prediction

In battery-powered devices, total resistance affects the battery life. By calculating the total resistance, engineers can estimate the battery’s discharge time and optimize the device’s power consumption.

Appliance Efficiency

Total resistance influences the efficiency of electrical appliances. By calculating the total resistance, manufacturers can design appliances to minimize power loss and improve their energy efficiency.

Lighting Control

In lighting circuits, total resistance controls the brightness of lamps. By adjusting the total resistance, engineers can dim or brighten lights to achieve the desired lighting levels.

Temperature Control

Total resistance is used in temperature control systems. By varying the total resistance of a heating element, engineers can regulate the temperature of a device or system.

Motor Speed Control

In electric motors, total resistance affects the speed of the motor. By calculating the total resistance, engineers can design motor controllers that provide the desired motor speed and torque characteristics.

How To Find The Total Resistance In A Circuit

The total resistance in a circuit is the sum of the resistances of all the resistors in the circuit. This can be calculated using the following formula:

“`
Total resistance = R1 + R2 + R3 + … + Rn
“`

Where R1, R2, R3, …, Rn are the resistances of the individual resistors in the circuit.

For example, if you have a circuit with three resistors, each with a resistance of 1 ohm, the total resistance in the circuit would be 3 ohms.

People Also Ask About How To Find The Total Resistance In A Circuit

What is the difference between resistance and impedance?

Resistance is a measure of the opposition to the flow of electric current, while impedance is a measure of the opposition to the flow of alternating current. Impedance is a more general term than resistance, and it includes resistance as well as other factors, such as inductance and capacitance.

How do you calculate the resistance of a parallel circuit?

The total resistance of a parallel circuit is given by the following formula:

“`
1/Total resistance = 1/R1 + 1/R2 + 1/R3 + … + 1/Rn
“`

Where R1, R2, R3, …, Rn are the resistances of the individual resistors in the circuit.

How do you calculate the resistance of a series circuit?

The total resistance of a series circuit is given by the following formula:

“`
Total resistance = R1 + R2 + R3 + … + Rn
“`

Where R1, R2, R3, …, Rn are the resistances of the individual resistors in the circuit.