A potential difference of 10V is needed to make a current of 0.02A flow through a wire. What potential difference is needed to make a current of 250mA flow through the same wire?

First case, Given,

Current, I = 0.02A Voltage, V = 10 volt

We know that, V = IR

10 = 0.02 × R

R = 10/0.02 = 500 Ohms

Second case,

Current, I = 250 × 10-3 A Resistance, R = 500 Ohm V = IR

V = 250 × 10-3 × 500 = 125 volt