The current through a wire decreases linearly from 10 A to 0 A over a time interval of 4 seconds. What is the total charge that flows through the wire during this time?

20 C
10 C
15 C
30 C

Correct answer: 20 C

Solution

Since current decreases linearly from 10 A to 0 A in 4 s, the i-t graph is a right triangle with base 4 s and height 10 A. Total charge = area = (1/2)*4*10 = 20 C.

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