Question

When two cells of e.m.f 1.5 V and 1.1 V connected in series are balanced on a potentiometer, the balancing length is 260 cm. The balancing length, when they are connected in opposition is (in cm) ____________.

Options

• 100

• 110

• 40

• 65

Answer 1

When two cells of e.m.f 1.5 V and 1.1 V connected in series are balanced on a potentiometer, the balancing length is 260 cm. The balancing length, when they are connected in opposition is (in cm) 40.

Explanation:

`"E" prop l`

`("E"_1 + "E"_2)/("E"_1 - "E"_2) = l_1/l_2`

`therefore (1.5 + 1.1)/(1.5 - 1.1) = 260/l_2`

`therefore 2.6/0.4 = 260/l_2`

`therefore l_2 = 260/2.6 xx 0.4`

` = 40  "cm"`