Shown an arrangement to measure the emf `(epsilon)`and internal resistance r of a battery. The voltmeter has a very high resistance and the ammeter also has some resistance.The voltmeter reads 1.52 V when the switch S is open.When the switch is closed the voltmeter reading drops to 1.45 V and the ammeter read 1.0A Find the emf and the internal resistance of the battery.

Explanation

(a) When switch is open no current pass
through the ammeter in the upper part of
the circuits as the volt meter has resistant.
Thus current in it is zero.
Voltmeter reads the emf (there is no
potential drop across the register),
(b) When switch is closed current passes
through the circuit the value of l.
The voltmeter reads
` epsilon - iR = 1.45 `
` rArr 1.52 - iR = 1.45 `
` rArr iR = 0.07`
` rArr 1.R = 0.07` .