Calculate the time in which 4.8 kJ of energy would be expended when an electric...

WAEC 1992

Calculate the time in which 4.8 kJ of energy would be expended when an electric heater of resistance 1.8 x 10³Ω is used on a 240 V mains supply. (Neglect heat losses to the surrounding).

A. 150.0s
B. 90.0s
C. 36.0s
D. 20.0s
E. 2.7s.

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Correct Answer: Option A

Explanation

E = V²t/R

t =

ER/V²

4800 x 1.8 x 10³/240 x 240

= 150s

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Calculate the time in which 4.8 kJ of energy would be expended when an electric...

Correct Answer: Option A

Explanation

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