A low voltage supply with an e.m.f. of 20 V and an internal resistance of 1.5 ohms is used to supply power to a heater of resistance 6.5 ohms in a fish tank. What is the power supplied to the water in the fish tank?
Correct answer: B. 41 W
- A. 50 W
- B. 41 W
- C. 53 W
- D. 62 W
Explanation
Explanation:Total resistance (R) = internal resistance (r) + heater resistance (R_heater) = 1.5 Ω + 6.5 Ω = 8 Ω. Current (I) = emf (ε) / R = 20 V / 8 Ω = 2.5 A. Power (P) = I²R_heater = (2.5 A)² × 6.5 Ω = 40.625 W ≈ 41 W.
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About Current Electricity
Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.
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