The potential difference between the two end terminals of an electric heater is 220 V and the current through it is 0.5 A. What would be the current through the heater if the potential difference across the terminals of the heater is reduced to 120 V?

Question

Question

This question was previously asked in

UPSC NDA-II (General Ability) Official Paper-I (Held On: 03 Sept, 2023)

Answer 1

Concept:

Ohm's Law:

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
Formula: V = I × R
Resistance (R): A measure of the opposition to current flow in an electrical circuit. SI Unit: Ohm (Ω).
Current (I): The flow of electric charge. SI Unit: Ampere (A). Formula: I = V / R
Voltage (V): The potential difference across the terminals of the heater. SI Unit: Volt (V).

Calculation:

Given,

Voltage across the heater, V₁ = 220 V

Current through the heater, I₁ = 0.5 A

Voltage across the heater after reduction, V₂ = 120 V

First, find the resistance of the heater using Ohm's Law:

R = V₁ / I₁

⇒ R = 220 V / 0.5 A

⇒ R = 440 Ω

Now, find the current through the heater when the voltage is reduced:

I₂ = V₂ / R

⇒ I₂ = 120 V / 440 Ω

⇒ I₂ = 0.2727 A

∴ The current through the heater is approximately 0.27 A when the potential difference is reduced to 120 V.