1.

In the above circuit, if the current reading in the ammeter A is 2A, what would be the value of R1? 

Answer»

5 ohm, 10 ohm and R1 are in series 

1/Rp = 1/5+1/10+1/R

1/Rp = (2+1)/10 + 1/ R1 

= 3/10 +1/ R

1/Rp = (3 R1 +10)/10 R

Rp= 10 R1 / (3 R1 +10) 

Now, 6 ohm, 6 ohm and Rp are in series 

Thus, 

Req = 12 + 10 R1 / (3 R1 +10) ------------------ (1) 

V = I Req 

From the circuit 

Req = 30/2 = 15 A ---------------(2) 

Equating (1) and (2)

12 + 10 R1 / (3 R1 +10) = 15 

10 R1 / (3 R1 +10) = 3 

10 R1= (9 R1 + 30) 

Thus, R1 = 30 ohm.



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