A battery of emf 12 V and internal resistance 2 `Omega` is connected to a 4 `Omega` resistor as shown in the Fig. Show that a voltmeter when placed across the cell and across the resistor, in turn, gives the same reading.

Explanation

Here emf of battery `epsi` =12 V, internal resistance r=2 `Omega` and external resistance R=4`Omega`
Circuit current `I = (epsi)/(r + R) = (12)/(2 + 4) = 2A`
` therefore ` Voltmeter reading when placed across the cell
`V_1 = epsi - Ir = 12 - 2 xx 2 = 8V`
and voltmeter reading when connected across the resistor
`V_2 = IR = 2 xx 4 = 8V`
Obviously `V_1 = V_2 = 8V`