The diagram of an electric circuit shows three parallel resistors. If R is the equivalent resistance of the three resistors, then 1/R = 1/R1 + 1/R2 + 1/R3.

Question

In this circuit R1 is twice the resistance of R2 and R3 equals 20 ohms. Suppose the equivalent resistance is equal to 10 ohms. Find R1 and R2.

Answer 1

1/10= 1/2R2 + 1/R2 +1/20

2R2 =10 +20 +R2

R2 =30 ohms

R1= 60 ohms

1/10 = 1/60 +1/30 +1/20