Question

Ten identical cells each of potential E and internal resistance r are connected in series to form a closed circuit. An ideal voltmeter connected across three cells. will read

(a) 10 E

(b) 3 E

(c) 13 E

(d) 7 E

Answer 1

Correct option (b) 3 E

Explanation:

Given: Initial number of cells (n1) = 10; Potential of each cell = E;

Internal resistance of each cell = r and

final number of cell (n2) = 3.

We know from the Ohm'* law, total voltage of ten cells = 10 x E = 10 E and total resistance in ten cells

= 10 x r = 10 r. Therefore current in the circuit,

or potential difference across three cell

( Since the voltmeter is ideal, therefore it will read 3 E).