Four identical bulbs, each with a filament resistance of 178 , are connected to

Question

Four identical bulbs, each with a filament resistance of 178 , are connected to a 50-V battery as shown in the diagram below. S1, S2, and S3 represent switches.

(a) If S1 and S2 are closed while S3 is open, what is the current through each bulb?

(b) If S3 is closed while S1 and S2 are open, what is the current through each bulb?

(c) If S2 and S3 are closed while S1 is open, what is the current through each bulb?

(d) If S1 and S3 are closed while S2 is open, what is the current through each bulb?

Explanation / Answer

A.

In this case, it's as if only Bulb 1 is there.

Thus,

I1 = V / R1 = 0.281 A
I2 = 0 A
I3 = 0 A
I4 = 0 A

B.

In this case, it will look like R1, R3, and R4 are in series, and R2 is not part of it.

Thus,

I1 = V / (R1 + R2 + R3) = 0.0936 A
I2 = 0 A
I3 = 0.0936 A
I4 = 0.0936 A

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