Question

if the resistance of circuit having 12v source is increased by 4ohm the current drop by 0.5A .what is the original resistance of the circuit​

Answer 1

The original resistance of the circuit = 8 ohm

Let the original resistance of the circuit be x.

Voltage source connected = 12 V

Initial current = I = V/R

I = (12/x) A

When the resistance in the circuit is increased by 4 ohm -

Final current = I - 0.5

Resistance = x+4

=> I - 0.5 = 12/(x+4)

=> 12/x - 0.5 = 12/(x+4)

=> 12/x - 12/(x+4) = 0.5

=> 96 = x² + 4x

=> x² + 4x + 96 = 0

=> x = 8 , -12

x = -12 will be rejected because resistance cannot be negative .

So, original value of resistance in the circuit is equal to 8 ohm.