Resistance of Light Bulbs in Parallel

  • Thread starter Angie K.
  • Start date
  • #1
108
1

Homework Statement


Eight lights are connected in parallel to a 110-V source by two long leads of total resistance 1.6 Ω.

a. If 302 mA flows through each bulb, what is the resistance of each?

b. What percent of the total power is wasted in the leads?

Homework Equations


V=I
P=V^2/R

R. The attempt at a solution

I found the total resistance to be 45.5298 V but when plugging that in to find the resistance of each bulb, I can't seem to get to the right answer. What am I missing here?
 

Answers and Replies

  • #2
Hesch
Gold Member
922
153

Homework Statement


Eight lights are connected in parallel to a 110-V source by two long leads of total resistance 1.6 Ω.

a. If 302 mA flows through each bulb, what is the resistance of each?

b. What percent of the total power is wasted in the leads?

Homework Equations


V=I
P=V^2/R

R. The attempt at a solution

I found the total resistance to be 45.5298 V but when plugging that in to find the resistance of each bulb, I can't seem to get to the right answer. What am I missing here?

It can be calculated in many ways (how did you do it?).

1) You can find the resistance in one bulb, (Rbulb=V/Ibulb), after that finding Rtotal in 8 bulbs in parallel.
2) You can find the total power, after that using Ptotal=V2/Rtotal
3) You can find the total current, after that using Rtotal=V/Itotal
 
Last edited:
  • #3
108
1
It can be calculated in many ways (how did you do it?).

1) You can find the resistance in one bulb, (Rbulb=V/Ibulb), after that finding Rtotal in 8 bulbs in parallel.

That is what I used
Rbulb=V/Ibulb
=110V/.302
=364.238 shouldn't that be the resistance of each bulb? Or do I have to find the voltage drop for eacg lightbulb?and divide it by the total current (wouldn't that just give me the resistance for all the bulbs?)
 
  • #4
Hesch
Gold Member
922
153
The voltage drop for each bulb is 110V (bulbs are in parallel). Your Rbulb is correct, and so is your Rtotal in #1.

But then I cannot understand this in #1:

but when plugging that in to find the resistance of each bulb, I can't seem to get to the right answer. What am I missing here?

What's your problem here?
 
Last edited:

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