What is Ohm’s Law ( Definition, Formula, Applications )

What is Ohm's law?

In this article we will read about What is Ohm’s Law in the chapter of Physics. This rule is very important. What is ohm’s law questions are asked in class 10 and class 12 and other competitive exams also.

Today I will give you complete information about the important Ohm’s law of 10th and 12th board physics. By reading this post, you will easily understand Ohm’s law and know its use.

What is Ohm’s law?

In 1827, the German physicist Georg Simon Ohm discovered the relationship between the electric current I in a metal wire and the potential difference between its ends. In an electric circuit, the potential difference between the two ends of a metal wire is proportional to the current flowing through it, this is called Ohm’s law.

Definition of Ohm’s law

Ohm’s law- in a closed D.C. In an electrical circuit, the voltage produced across a conductor is proportional to the current flowing through it. This is called Ohm’s law.

V∝ I


Ohm’s law is applicable only in DC circuits, not in AC circuits.


According to Ohm’s law, if the physical state (length, thickness, temperature etc.) of a conductor is not changed, the potential difference across the conductor is proportional to the current flowing through that conductor.

Ohm’s law describes the relationship between potential or voltage, current, and resistance.

Ohm’s Law Formula


This is the basic meaning of Ohm’s law, from this formula you can define the law


V = voltage

I = Current

R = resistance of the circuit

simple language in Ohm’s law

Ohm’s law states that in a closed circuit, current is directly proportional to voltage and inversely proportional to resistance when its physical states are the same, such as temperature, etc., so Iαv, lαl/R, or R= V/I or V=IR or

I = V/R

Suppose the resistance of a circuit is 10 ohms and the voltage is 200 volts, then we can find its current.

I =V/R

I =200/10=20 amps

Now if the current and voltage are given in the above circuit, then the resistance can be easily obtained.

R = V/I Ohm

R= 200/20 = 10 ohm

Then if the current and resistance are given in the circuit, then the voltage can be easily removed.

V = I.R. V=20 x 10 = 200 volts


Limitations Ohm’s Law

Ohm’s law is valid for a wide class of substances, there exist some materials and devices used in electric circuits where the proportionality of V and I does not apply. Broadly speaking, this deviation can be of one or more of the following types-

(a) V loses its proportionality to I

(b) The relation between V and / depends on the sign of V. In other words, if the current for some . So, keeping the magnitude of v constant and changing its direction, in the opposite direction. A current of equal magnitude is not produced. For example, this happens in diodes.

(c) The relation between V and / is not the only relation i.e. there can be more than one value of V for the same current I. Materials and devices that do not obey Ohm’s law as an equation are, in fact, widely used in electronic circuits. However, in this chapter and subsequent chapters, we will study electric current in a material that obeys Ohm’s law.

Verification of Ohm’s Law

This principle of om ka niyam shows that the resistance of a conductor remains constant. That is, if the voltage is doubled, the current in the conductor will also be doubled. But the opposition will remain the same.

Keep in mind that all these things are valid as long as the temperature of the conductor remains constant. If the temperature increases, the resistance will also increase.

Uses of Ohm’s Law

This principle is very useful in solving simple circuits. The whole circuit would have been one that forms a closed loop. If there is one voltage source in the circuit and one component that consumes current, the total of all voltages in that loop will be zero (0).

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Examples of Ohm’s Law

Examples of ohm’s law
Q. A DC motor which is getting 12 volt supply, its total resistance is 6 ohm, then what will be the value of current flowing in the circuit?


voltage = 12

Resistance = 6

Then, according to Ohm’s law

V = IR

12 = 6×I

I = 12/6

I (current) = 2 amps

Q. Find the resistance of a conducting wire, if a current of 0.5 ampere is passed through it, a potential difference of 2 volts is produced at its ends.


Current (I) = 0.5 Ampere
Potential difference (V) = 2 volts
Resistance (R) = ?

R = V/I
R = 2/0.5 = 4 ohm

Q. On passing 0.5 ampere current in an electric bulb, 220 volt potential difference is produced, then find the value of resistance.


Current (I) = 0.5 Ampere
Potential difference (V) = 220 volts
Resistance (R) = ?

R = V/I
R = 220/0.5 = 440 ohm

Q. If the resistance of the filament of an electric bulb is 1200 , then how much current will this bulb draw from a 220V source?
If the resistance of the coil of an electric heater is 100 , then how much current will this electric heater 200V source draw?


V = 220 volts
R = 1200
Y(B) V = 220V
R = 100

I= V/R
I = 220/100 = 2.2 A

Questions Related to Ohm’s Law

What is Ohm’s law?

  • When the potential difference across the conductor is 1 volt and the current flowing in the conductor is 1 ampere, the resistance of the conductor will be 1 ohm.

Do semiconductors obey Ohm’s law?

  • Ohm’s law is not obeyed in semiconductors.

What is the unit of Ohm?

  • Resistance

Ohm’s law was propounded by which scientist?

  • In 1826, the German scientist Dr. Georg Simon Ohm


We hope that What is Ohm’s law, Definition of Ohm’s law, Ohm’s Law Formula, simple language in Ohm’s law, Limitations Ohm’s Law, Uses of Ohm’s Law, must have been understood. You must have got the answer of all these questions very well.

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