A battery of emf 24 V is connected to a 6.0- $\Omega$ resistor.As a result, current of 3.0 A exists in the resistor.The rate at which energy is being dissipated in the battery is:
A)3.0 W
B)6.0 W
C)18 W
D)54 W
E)72 W

Question

A battery of emf 24 V is connected to a 6.0- $\Omega$  resistor.As a result, current of 3.0 A exists in the resistor.The rate at which energy is being dissipated in the battery is:
A)3.0 W
B)6.0 W
C)18 W
D)54 W
E)72 W

Quizplus · Accepted Answer

The rate at which energy is being dissipated in the resistor is given by P=I^2*R, where I is the current and R is the resistance. Therefore, P = (3.0 A)^2 * 6.0 Ω = 54 W. 
However, the battery is the source of this energy, so the rate at which energy is being dissipated in the battery is the same. Therefore, the answer is 54 W, which is closest to choice C (18 W).

A Battery of Emf 24 V Is Connected to a 6.0-