# A household circuit rated at 120 Volts is protected by a fuse rated at 15 amps. What is the maximum number of 100 watt light bulbs?

A household circuit rated at 120 Volts is protected by a fuse rated at 15 amps. What is the maximum number of 100 watt light bulbs which can be lit simultaneously in parallel in this circuit without blowing the fuse?

### 6 Answers

- billrussell42Lv 75 months agoFavorite Answer
one bulb draws a current of

P = EI

100 = 120I

I = 100/120 = 5/6 amp

15 amps / (5/6 amp/bulb) = 15•6/5 bulb = 18 bulbs

(this is school problem answer)

but fuses and bulbs have tolerances, so you need to reduct that to 16-17

- M.Lv 75 months ago
My selfish, safe, personal opinion is:

15 amp, 14 gauge wiring, times 80% equals 12 continuous amps, 24 hours per day.

Pretending that there is a true 100 watt bulb and 120 volts, such a bulb will draw .8333 amps.

So, 12 usable amps divided by .8333 amps equals 14.4 bulbs.

So MY answer is 14 bulbs.

24/7. No overload.

1400 watts total.

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8-304(c) "Where the connected load is known, the number of outlets shall be permitted to exceed 12, provided that the load current does not exceed 80% of the rating of the overcurrent device protecting the circuit."