The mechanical equivalent of heat is 1 cal = 4.18 J. A heating coil, connected to a 120-V source, develops 60,000 calories in 10 minutes. The current in the coil is:
A) 0.83 A
B) 2 A
C) 3.5 A
D) 20 A
E) 50 A

Question

Quizplus · Accepted Answer

First, convert calories to joules: 60,000 cal * 4.18 J/cal = 250,800 J. Power (P) is energy/time, so P = 250,800 J / 600 s = 418 W. Using P = VI, where V = 120 V, I = P/V = 418 W / 120 V = 3.48 A, approximately 3.5 A.

The Mechanical Equivalent of Heat Is 1 Cal = 4