Question

A current of 0.2a ,flows through a circuit containing a battery and a resistor r when a wire of 2 ohms is connected in parallel with the resistor the current in the circuit becomes 1.3a . find the resistance of the resistor r

Answer 1

Current= 0.2A
Resistance of wire=2ohms
As V=IR
V=0.2 x 2
V=0.4 volts
Let resistance of the resistor r be x
So when in parallel connection resistance =1/2 + 1/x
V=IR
0.4= 1.3 x (1/2 +1/x)
0.4/1.3=1/2+1/x
4/13-1/2=1/x
8/26-13/26=1/x
-5/26=1/x
-5x=26
x=26/-5
x=-5.2ohms