Question

What will happen if a student while studying the dependence of current on the potential difference keeps the circuit closed for a long time to measure the current and potential difference?

Answer 1

If the circuit is kept closed for a long time t resistor will get heated up and its value will change. This is because heat produced in any resistor, 

H = I²Rt 

As time will increase heat produced will increase. 

Hence resistor will get heated up due to which its value will change.