Electronics Articles

Ohm’s Law: Statement, Formula, Solved Examples, Verification, and FAQs

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Key Points

  • Ohm’s Law is a fundamental principle in electrical engineering, relating voltage (V), current (I), and resistance (R) in a linear conductor. It was formulated by Georg Simon Ohm in 1827.
  • The mathematical expression of Ohm’s Law is V = I × R, where V represents voltage (in volts), I represents current (in amperes), and R represents resistance (in ohms). It can also be rearranged to find current or resistance.
  • Ohms Law can be experimentally verified by measuring V, I, and R in a circuit and plotting V against I. Visual aids like the Ohms Law Triangle, Pie Chart, and Matrix Table can help in calculations and references.
  • Ohm’s Law is widely used for determining circuit values, voltage drops, and power calculations. However, it is not applicable to non-linear devices like diodes and has limitations with components that don’t follow a constant voltage-to-current ratio.

Ohm’s Law is a fundamental principle in the field of electrical and electronic engineering. It governs the relationship between voltage, current, and resistance in an electric circuit.

This article provides an in-depth understanding of Ohms Law, its statement, formula, solved examples, verification, and frequently asked questions.

We have carefully written this article to be concise, ensuring that you gain a thorough understanding of this essential concept.

Introduction to Ohm’s Law

Ohm’s Law is named after the German physicist Georg Simon Ohm, who first formulated it in 1827. It emphasizes that the current flowing through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance of the conductor. In simple terms, Ohms Law describes the relationship between voltage (V), current (I), and resistance (R) in an electric circuit.

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Mathematically, Ohm’s Law can be expressed as:

V = I × R

Where:

  • V represents voltage, measured in volts (V)
  • I represents current, measured in amperes (A)
  • R represents resistance, measured in ohms (Ω)

It is important to note that Ohm’s Law is only applicable to linear conductors, meaning that the resistance remains constant with changes in voltage and current. Non-linear conductors, such as diodes and transistors, do not follow Ohms Law.

Ohm’s Law Statement

Ohm’s Law states that the current (I) flowing through a conductor is directly proportional to the voltage (V) applied across it and inversely proportional to the resistance (R) of the conductor, provided that the temperature remains constant. In other words, increasing the voltage across a conductor will result in an increase in current, while increasing the resistance will result in a decrease in current.

Ohm’s Law Formula

The formula for Ohms Law can be derived from its statement. As mentioned earlier, Ohm’s Law can be expressed mathematically as:

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V = I × R

By rearranging the formula, we can also find the current (I) and resistance (R) in a circuit:

I = V ÷ R

R = V ÷ I

These three equations form the basis of Ohm’s Law calculations and can be used to determine the unknown value of voltage, current, or resistance in a circuit, provided that the other two values are known.

Ohm’s Law Triangle

To help remember the Ohms Law formulas, a triangle, often called the Ohm’s Law Triangle, can be used as a visual aid. The triangle has voltage (V) at the top, current (I) at the bottom left, and resistance (R) at the bottom right.

Ohm’s Law Triangle

To find the unknown value, cover the corresponding symbol in the triangle, leaving the other two symbols visible. For example, to calculate voltage, cover the V symbol, revealing I and R, which indicates the formula V = I × R.

Solved Examples of Ohm’s Law

Example 1: Finding Voltage

A current of 5 A flows through a resistor with a resistance of 10 Ω. Calculate the voltage across the resistor.

Using the formula V = I × R:

V = 5 A × 10 Ω = 50 V

The voltage across the resistor is 50 V.

Example 2: Finding Current

A voltage of 120 V is applied across a resistor with a resistance of 60 Ω. Calculate the current flowing through the resistor.

Using the formula I = V ÷ R:

I = 120 V ÷ 60 Ω = 2 A

The current flowing through the resistor is 2 A.

Example 3: Finding Resistance

A voltage of 24 V is applied across a conductor, and a current of 3 A flows through it. Calculate the resistance of the conductor.

Using the formula R = V ÷ I:

R = 24 V ÷ 3 A = 8 Ω

The resistance of the conductor is 8 Ω.

Verification of Ohm’s Law

Ohm’s Law can be verified experimentally by measuring the voltage, current, and resistance in a simple circuit consisting of a power source (such as a battery), a resistor, and an ammeter and voltmeter.

By varying the voltage across the resistor and measuring the resulting current, a plot of voltage versus current can be created. If the plot is a straight line, it confirms that the conductor follows Ohm’s Law.

It is essential to ensure that the temperature remains constant throughout the experiment, as temperature changes can affect the resistance of the conductor and invalidate the verification of Ohms Law.

Calculating Electrical Power Using Ohm’s Law

Electrical power (P), measured in watts (W), is the rate at which energy is converted or consumed in a circuit. It can be calculated using the following formula:

P = V × I

By substituting Ohm’s Law formulas, electrical power can also be calculated based on voltage and resistance or current and resistance:

P = V² ÷ R

P = I² × R

These equations can be used to determine the electrical power consumed or generated by components in a circuit.

Ohm’s Law Pie Chart

Another useful visual aid for Ohms Law is the pie chart, which condenses all the equations for voltage, current, resistance, and power into a single diagram.

Ohms Law Pie Chart

The pie chart can be a helpful reference tool when calculating unknown values in a circuit.

Ohm’s Law Matrix Table

Like the Ohm’s Law Pie Chart, the equations can also be organized into a matrix table for easy reference.

Ohm’s Law Matrix Table

Ohm’s Law Applications

The main applications of Ohm’s Law include:

  • Determining the voltage, resistance, or current of an electric circuit.
  • Maintaining the desired voltage drop across electronic components.
  • Using Ohms Law in DC ammeters and other DC shunts to divert current.

Limitations of Ohm’s Law

Ohm’s Law has some limitations:

  • It is not applicable for unilateral electrical elements like diodes and transistors, which only allow current to flow in one direction.
  • Non-linear electrical elements with varying capacitance, resistance, or inductance may not have a constant voltage-to-current ratio, making it difficult to use Ohm’s Law.

Frequently Asked Questions (FAQs)

Q1: What does Ohm’s Law state?

Ohm’s Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance of the conductor.

Q2: What can Ohm’s Law be used for?

Ohm’s Law is used to determine the values of voltage, current, and resistance in a circuit, as well as to calculate the electrical power consumed or generated by components.

Q3: Is Ohm’s Law universal?

No, Ohms Law is not universal. It is only applicable to ohmic conductors, such as copper or iron, but not to non-ohmic conductors like semiconductors.

Q4: Why is Ohms Law not applicable to semiconductors?

Ohm’s Law doesn’t apply to semiconducting devices because they are nonlinear devices, meaning that the ratio of voltage to current doesn’t remain constant for variations in voltage.

Q5: When does Ohms Law fail?

Ohm’s Law fails to explain the behavior of semiconductors and unilateral devices like diodes. It may not give the desired results if physical conditions such as temperature or pressure are not kept constant.

Wrapping Up

Ohms Law is a fundamental principle in electrical and electronic engineering, governing the relationship between voltage, current, and resistance in an electric circuit. Understanding Ohm’s Law is essential for anyone working with electrical circuits, as it provides the basis for calculating unknown values and analyzing circuit behavior.

By mastering the Ohm’s Law formulas, Triangle, and Pie chart, as well as understanding its applications and limitations, one can become proficient in using Ohms Law to solve a wide range of electrical problems.

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Boateng

Boateng Oduro is passionate about learning new technologies and working on them. He is a teacher and an engineer who loves to read, write, and teach. He's always curious about things and very determined to track the latest technologies and the trends for the future.

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