A student kept her 60-watt, 120-volt study lamp turned on from 2:00 PM until 2:00 AM. How many coulombs of charge went through it?
A) 150
B) 3,600
C) 7,200
D) 18,000
E) 21,600

Question

Quizplus · Accepted Answer

To find the charge in coulombs, first calculate the current using P = VI, where P = 60 watts and V = 120 volts. This gives I = 0.5 A. The lamp was on for 12 hours, which is 43,200 seconds. Charge Q = I × t = 0.5 A × 43,200 s = 21,600 C.

A Student Kept Her 60-Watt, 120-Volt Study Lamp Turned on from 2:00