One of the basic laws of Physics is Ohm’s law. It gives the relationship between electric current and potential difference. Ohm’s law was experimentally verified by a German physicist Georg Simon Ohm.

Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperature remain constant.

V=IR

In the equation, the constant of proportionality: R, is Resistance and has units of ohms, with the symbol Ω. We can rewrite the formula in order to calculate the current and resistance, respectively, as follows:

I=V/R

or

R=V/I

If the temperature and the other physical factors remain constant, Ohm’s law holds true.

This continuous movement of electric charge through the conductors of a circuit is called a current. The force motivating charge carriers to flow in a circuit is called voltage. This opposition to the motion of charges is more appropriately called resistance. The standard units of measurement for electrical current, voltage, and resistance are Ampere, volt, and Ohm.

Power is given by the formula using voltage and current:

P=VI

When the values for voltage and resistance are given:

When the values for current and resistance are given:

Applications of Ohm’s law:

• Ohm’s law is used to find an electric circuit’s voltage, resistance, or current.
• Ohm’s law is used to maintain the desired voltage drop across the electronic components.
• Ohm’s law is used in DC ammeter, and other DC shunts to divert the current.

The limitations of Ohm’s law are:

• Ohm’s law is not applicable for unilateral electrical elements like diodes and transistors as they allow the current to flow through in one direction only.
• For non-linear electrical elements with parameters like capacitance, resistance, etc., the voltage and current won’t be constant with respect to time, making it difficult to use Ohm’s law.

Important Ohm’s Law Questions with Answers

1. What is the unit of measurement of current?

1. Meter
2. Volt
3. Ohm
4. Ampere

Answer: d) Ampere

Explanation: The unit of measurement of current is Ampere.

2. State true or false: Ohm’s law is universal.

1. TRUE
2. FALSE

Answer: FALSE.

Explanation: Ohm’s law is not universal since it is not applicable for non-ohmic conductors like semiconductors.

3. Fill in the blanks: current-voltage relationship is given by the formula _____

Answer: V=IR

4. Ohm’s law is named after which scientist?

It is named after the scientist Georg Simon Ohm.

5. _____ volt of pressure is needed to push one amp of current through one ohm of resistance.

1. Zero
2. One
3. Two
4. Three

Answer: b) One

6. Current density is represented by the alphabet.

1. C
2. D
3. I
4. J

Answer: d) J

Explanation: Current density is represented by the symbol ‘J’.

7. The SI unit of electrical resistance is the _____

1. Kelvin
2. Volt
3. Ohm
4. Ampere

Answer: c) Ohm

8. Fill in the blanks: The electrical conductance is measured in _____

Answer: Siemens

9. State true or false: The lightbulb filament violates Ohm’s Law.

1. TRUE
2. FALSE

Answer: TRUE

Explanation: Temperature rises as the current increases in the filament; hence it violates Ohm’s law.

10. The unit of power is

1. Siemens
2. Volts
3. Watts
4. Kelvin

Answer: c) Watts

Practice Questions

1. State and explain Ohm’s law.
2. Give the formula to calculate the power using voltage and current.
3. List the applications of Ohm’s law.
4. Can we apply Ohm’s law to diodes and transistors?
5. State true or false: Ohm’s law holds good only if the provided temperature and the other physical factors remain constant.

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