2. Some light bulbs are connected in parallel to a 120 V source as shown in the

Question

2. Some light bulbs are connected in parallel to a 120 V source as shown in the figure. Each bulb dissipates an average power of 75 W. The circuit has a fuse F that burns out when the current in the circuit exceeds 12 A. (a) Are these bulbs wired in- -series or -parallel (Vcheck to answer)? (b) Determine the maximum number of bulbs, which can be used in this circuit without burning out the fuse; (c) determine the current that flows through each of the light bulbs; and (d) what is the resistance of a single light bulb? 120 V

Explanation / Answer

Given,

V = 120 V ; P = 75 W

a)Parallel

b)We know that,

P = V^2/R => R = V^2/P

R = 120^2/75 = 192 Ohm

Let N be the number of the bulbs

I = 12/N

so. 192 x (12/N)^2 = 75 => N = 19.2

Hence, N = 19

c)I = 120/192 = 0.625 A

Hence, I = 0.625

d)R(single) = 192 Ohm

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