The length of a wire of a potentiometer is 100 cm and the e.m.f. of its standard cell is E volt. It is employed to measure the e.m.f. of a battery whose internal resistance is If the balance point is obtained at cm from the positive end, the e.m.f. of the battery is :
where i is the current in the potentiometer wire
As we learnt in
Potential gradient -
- wherein
internal resistance
Equation of cell -
- wherein
Potential gradient along wire
For battery
= E.m.f. of battery
Where current is drawn from battery.
Option 1)
This option is incorrect.
Option 2)
This option is incorrect.
Option 3)
where i is the current in the potentiometer wire
This option is correct.
Option 4)
This option is incorrect.
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