Question

5. In the given figure, if galvanometer shows null
deflection then emf of each cell will be
+5V, 18
+ 2m →
10 m,92 B
E &
(1) 9V
(3) 4.5 V
(2) 0.9 V
(4) 1.8 V​

Answer 1

Answer:(2) 0.9

Explanation

Solve this in two separate steps by breaking the circuit in two parts -

(1) lower part which contains the cell to find relation between emf E and Vab

(2) upper part to calculate current and value of potential across ab

Answer 2

Emf of each cell will be 0.9 V.

Explanation:

Galvanometer shows no deflection. It is a balanced current flowing through the wire.  

i = 5 / (9 + 1) = 0.5 A

Voltage drop across the point A and the jockey is the emf of the battery.

E = (9 / 10 * 2) * 0.5 = 0.9 V

Emf of each cell will be 0.9 V.

Option 2 is the answer.