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(c27p74)The figure shows a circuit containing three switches, labelled S1, S2, a

ID: 3161392 • Letter: #

Question

(c27p74)The figure shows a circuit containing three switches, labelled S1, S2, and S3. Find the current at "a" for all possible combination of switch settings. Put e = BO v, RI = 15 omega and R2 = 10 omega. Assume that at the battery has no resistance. Current at "a" for S1 and S2 and S3 open Current at "a" for S1 closed and S2 and S3 open Current at "a" for S1 and S2 closed S3 open Current at "a" for S1 and S2 and S3 closed Current at "a" for S1 and S3 closed and S2 open Current at "a" for S3 closed and S1 and S2 open

Explanation / Answer

Here, when all S1 , S2 , S3 are all open ,

as the circuit is not complete ,

the current at a is ZERO

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when S1 is closed

for the equivalent resitance

Req = 2 * R1 = 2 * 15 = 30 Ohm

current at a = E/Req

current at a = 80/30 A

current at a = 2.67 A

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when S1 and S2 is closed

when S1 is closed

for the equivalent resitance

Req = 1/(1/(R1 + R2) + 1/R1) + R1

Req = (1/(15 + 10) + 1/15) + 15

Req = 15.1 Ohm

current at a = E/Req

current at a = 80/15.1 A

current at a = 5.30 A

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when all S1 , S2 , S3 are all closed

for the equivalent resitance

R3 = R1 + R2 = 10 + 15 = 25

R4 = 25 * 15/(15 + 25) = 9.4 Ohm

R5 = 9.4 + 10 = 19.4 Ohm

R6 = 19.4 * 15/(19.4 + 15)

R6 = 8.46 Ohm

Req = 8.46 + 15 = 23.46 Ohm

current at a = E/Req

current at a = 80/23.46 A

current at a = 3.41 A

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please post rest in a seperate question