Four identical light bulbs are connected ei- ther in series (circuit A), or in a

Question

Four identical light bulbs are connected ei- ther in series (circuit A), or in a parallel-series combination (circuit B), to a constant voltage battery with negligible internal resistance.

Assuming the battery has no internal re- sistance and the resistance of the bulbs is temperature independent, what is the ratio of the total power consumed by circuit A to that

consumed by circuit B; i.e., ?? P(A)total /?? P(B)total ??

Options are: 2, 8, 16, 1/16, 1/2, 1/squr.8, 1/4, 4, or 1

Do you know which option is correct?

Explanation / Answer

eq resistance in case all are in series = r+r+r+r = 4r

power consued = V^2/4r

in case all are in parallel

1/req = 1/r+1/r+1/r+1/r

1/req = 4/r

req = r/4

Power consumed = 4 V^2 / R

power series / power parallel = [V^2/r] / [4 V^2/r]

power series / power parallel = 1/4

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