A certain 20-A circuit breaker trips when the current in it equals 20 A.What is the maximum number of 100-W light bulbs you can connect in parallel in an ideal 120-V dc circuit without tripping this circuit breaker?
A)11
B)17
C)23
D)27

Question

Quizplus · Accepted Answer

We can use the formula P = VI to find the current drawn by each 100-W light bulb:
P = 100 W, V = 120 V, so I = P/V = 100/120 = 5/6 A
The total current drawn by n light bulbs connected in parallel is:
I_total = n * I = 5/6 * n
To avoid tripping the 20-A circuit breaker, we need to have:
I_total <= 20 A, which translates to:
n <= 20*6/5 = 24
However, we need to round down to the nearest integer because we cannot connect a fractional number of light bulbs. Therefore, the maximum number of 100-W light bulbs we can connect without tripping the circuit breaker is 23 (since 24 would exceed the 20-A limit).

A Certain 20-A Circuit Breaker Trips When the Current in It