An electric heater does 200 J of work in 2 seconds. Find the resistance of the electric heater if the current in the circuit is 2 A.

  1. 5 Ω
  2. 10 Ω
  3. 20 Ω
  4. 25 Ω 

Answer (Detailed Solution Below)

Option 4 : 25 Ω 
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NDA 01/2025: English Subject Test
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Detailed Solution

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CONCEPT:

  • Heating effect of electric current: When a current is flowing in a circuit having resistance there is a heat dissipation due to the resistance. This is called the heating effect of electric current.
  • The heat dissipated is given by:

Heat (H) = I2 R t

Where I = the current flowing in the circuit, R = the resistance of the circuit, and t = the time taken

EXPLANATION:

Given that: current (I) = 2 A

Resistance = R

Heat dissipated = work done by the heater (H) = 200 J

Time (t) = 2 sec

Heat (H) = I2 R t = 22 × R × 2 = 200 J

8 R = 200

Resistance of the heater (R) = 200/8 = 25 Ω 

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