SAT Subject Physics Practice Question 89: Answer and Explanation

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Question: 89

7. How much energy is dissipated as heat in 20 s by a 100 Ω resistor that carries a current of 0.5 A ?

A. 50 J
B. 100 J
C. 250 J
D. 500 J
E. 1,000 J

Correct Answer: D

Explanation:

The equation P = I2R gives

P = (0.5 A)2(100 Ω) = 25 W = 25 J/s

Therefore, in 20 s, the energy dissipated as heat is

E = Pt = (25 J/s)(20 s) = 500 J

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