Ohm’s Law Formula 

Ohm’s Law is a fundamental principle in electrical engineering and physics that relates the current flowing through a conductor to the voltage across it and the resistance of the conductor. It states that the current (I) in a circuit is directly proportional to the voltage (V) and inversely proportional to the resistance (R), given by the equation I = V/R. This law provides a mathematical relationship between these three quantities and allows us to calculate one parameter when the other two are known. Ohm’s Law is widely used in the design and analysis of electrical circuits, and it forms the basis for understanding the behavior of resistive elements in electronic devices.
Consider two beakers that are connected by a pipe. One of the beakers is placed at a height above the other.

What is Ohm’s law?

Due to the height difference, the water will flow from the beaker placed higher to the beaker placed lower.

Beakers at different heights

If the height difference is increased, the flow of water will be even faster. Hence, the flow of water is directly proportional to the height difference

Flow ∝ height … (a)

Also, if the pipe is made thinner then the flow of water will slow down.

Increasing the thinness of the pipe

Hence the flow is inversely proportional to thinness.

Flow ∝ 1/thinness … (b)

Combining the statements (a) and (b),

Flow = height/thinness … (ignoring the constants)

Thus, the flow is directly proportional to the height difference and inversely proportional to the thinness.

Now, we can compare the flow of water to the flow of current (I), where the height difference is analogous to the voltage or potential difference (V), and the thinness is analogous to the resistance (R).

So, v = I/R

This is Ohm’s law which states that the flow of current is directly proportional to the potential difference.

Ohm’s Law Formula

The different equations of Ohm’s law can be easily remembered with the help of Ohm’s law triangle as shown below.

SI unit of Resistance is Ohm and is represented by the Greek letter omega (Ω).

The SI units of voltage and current are volt and ampere respectively.

Hence if the potential difference across two ends of a conductor is 1 V and the current through it is 1 A, then the resistance of the conductor will be 1 ohm.

Thus, 1 Ohm = 1 Volt / 1 Ampere.

Solved examples on Ohm’s Law Formula

Example 1: A current of 0.8 A flows through the resistor shown in the figure. The potential difference is given to us as 16 Volts. What is the resistance of the resistor?

Figure 1

Given:
Electric current(I) = 0.8A

Potential difference(V)= 16 v

To find: Resistance (R)

Formula:

V= IR

Solution:

Therefore, the resistance of the resistor is 20 ohms.

Example 2: How much current will an electric bulb draw from a 120 V source, if the resistance of the bulb filament is 1000 Ω?

Figure 2

Given:

Resistance (R) = 1000

Potential difference (V) = 120

To find: Electric current (I)

Formula:
V =IR

Solution:

Therefore, the electric bulb will draw 0.12 Ampere of current.

Example 3: How much current will an electric heater coil draw from a 120 V source, if the resistance of the heater coil is 100 Ω?

Figure 3

Given:

Resistance (R) = 100 Ω

Potential difference (V) = 120 V

To find: Electric current (I)

Formula: V=IR

Solution:

Therefore, the electric bulb will draw 1.2 Ampere of current.

Frequently Asked Questions on Ohm’s Law Formula

What is Ohm's Law?

Ohm's Law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, given a constant resistance. It is expressed mathematically as V = IR, where V represents voltage, I represents current, and R represents resistance.

Who discovered Ohm's Law?

Ohm's Law was formulated by the German physicist Georg Simon Ohm in 1827. He discovered the relationship between voltage, current, and resistance while studying the flow of electricity through conductors.

What are the units used in Ohm's Law?

In Ohm's Law, voltage is measured in volts (V), current is measured in amperes (A), and resistance is measured in ohms (Ω).

How can Ohm's Law be applied to circuits?

Ohm's Law is widely used in electrical and electronic circuits to analyze and design circuits. It helps determine the voltage, current, or resistance values in a circuit when the other two are known. By rearranging the equation, you can solve for any of the variables in the equation V = IR.

Does Ohm's Law apply to all types of conductors?

Ohm's Law is primarily applicable to conductors that have a constant resistance over a wide range of applied voltages and currents. However, it may not hold true for certain non-linear devices, such as diodes and transistors, which have complex voltage-current relationships.

Can Ohm's Law be used for AC (alternating current) circuits?

Ohm's Law can be used for AC circuits, but with some modifications. In AC circuits, the voltage, current, and resistance are represented as complex numbers or phasors, taking into account the phase differences between voltage and current. The relationship between voltage, current, and impedance (the AC equivalent of resistance) is described by complex impedance.

Are there any limitations to Ohm's Law?

Ohm's Law assumes that the resistance remains constant and that the conductor follows Ohm's Law linearly. In reality, there may be variations in resistance due to factors such as temperature changes or non-linear behavior in certain devices. Additionally, Ohm's Law is most accurate for metallic conductors and may not be as accurate for other types of materials