Practice MCAT Question - Q42 - Answer!
A 12 Ohm load is connected across a 6.0 V dc source. How much energy does the load use in half an hour?
A. 1.5 x 10-3 kWh
B. 2.0 x 10-3 kWh
C. 3.0 x 10-3 kWh
D. 12 x 10-3 kWh
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The correct answer is (A). The energy used by a load is the product of the power it uses per unit time and the length of time it is operated:
E = W = Pt = V2t/R
= (6.0 V)2 (0.50 h) / 12 Ohm
= 1.5 x 10-3 kWh
