# 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?

Relevance

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

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

• Login to reply the answers
• The electrical code says 12.

• Sean K
Lv 5
6 months agoReport

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."

• Login to reply the answers
• 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.

1400 watts total.

• Login to reply the answers
• 120*15/100 =18

• Login to reply the answers
• Login to reply the answers
• Login to reply the answers