Four cells, a thin wire AB, a voltmeter, an ammeter, a plug key and some thick connecting wires are taken. Th…

Four cells, a thin wire AB, a voltmeter, an ammeter, a plug key and some thick connecting wires are taken. The circuit is set up as shown below. The key is inserted into the plug and readings of ammeter (I) and voltmeter (V) are noted. Then the plug key is removed. Now two cells are connected in the circuit in series. Plugging in the key the new values of ‘V’ and ‘I’ are noted. The experiment is repeated by connecting three cells in series and then four cells. In each case ‘V’ and ‘I’ are noted.