Question

A parallel combination of 3 resistors takes a net current of 7.5A from a supply of 30 V. If 2 resistors are 10 ohm and 12 ohm.Find third resistor

Answer 1

The resistance of the group of 3 resistors is equal to

R = 30 V / 7.5 A = 4 ohm.

Let R3 be the resistance of the third resistor, then

1/R = 1/10 + 1/12 + 1/R3

so,

1/4 = 1/10 + 1/12 + 1/R3

1/R3 = 1/4 - 1/10 - 1/12
= 15/60 - 6/60 - 5/60
= 4/60

hence ,

R3 = 60/4 = 15 ohm