Potentiometer

[Niha afzal]

In these kinda questions my teacher taught me whenever the galavanometer shows zero current the voltage frm both batteries must be cancelling out .. I.e the emf of above and down battery both is same .... clearly the ans is B ..

BUT what I wana know is how do the voltage gets cancelled? Thats not possible right a tiny charge carrying energy on it how can the energy disappear?

Edited March 27, 2016 by Niha afzal

[studiot]

The energy doesn't disappear.

(But that was a reasonable question)

 

Current is rate of change or movement of charge.

So if the current is zero then there is no movement of charge.

If there is no movement of charge ie no current there is no change in energy.

 

Voltage (by itself) is not energy.

 

A battery that is not connected does not loose energy (except for leakage and old age)

But once you connect a circuit, charge flows as a current and the battery looses energy to the circuit.

 

Two equal voltages in opposition yield a net zero voltage in the same way that two equal forces in opposition in mechanics yield a net zero force.

If the net force is zero, nothing moves and no work is done.

The statement no work is done means there is no change of (mechanical) energy.

[Niha afzal]

Oooh soo I wasnt considering the NET EFFECT.. hmmmn got it and bcz of the net being zero the galvanometer doesnt show any reading

Edited March 27, 2016 by Niha afzal