Some light bulbs are connected in parallel to a 120 V source as shown in the figure. Each bulb dissipates an average power of 60 W. The circuit has a fuse F that burns out when the current in the circuit exceeds 9 A. Determine the largest number of bulbs, which can be used in this circuit without burning out the fuse.
A)9
B)17
C)25
D)34
E)36

Question

Some light bulbs are connected in parallel to a 120 V source as shown in the figure. Each bulb dissipates an average power of 60 W. The circuit has a fuse F that burns out when the current in the circuit exceeds 9 A. Determine the largest number of bulbs, which can be used in this circuit without burning out the fuse. 
A)9 
B)17 
C)25 
D)34 
E)36

Quizplus · Accepted Answer

The total power consumed by the light bulbs will be P = n*60, where n is the number of bulbs. Using the formula for power in a circuit, P=VI, and the fact that the circuit is in parallel, we can find the total current in the circuit: P = VI -> I = P/V -> I = (n*60)/120 = n/2 To prevent the fuse from burning out, the current in the circuit must not exceed 9 A. Therefore, we can set up the inequality: n/2 <= 9 n <= 18 The largest integer value of n that satisfies this inequality is 17, so we can use 17 bulbs without burning out the fuse.

Some Light Bulbs Are Connected in Parallel to a 120