Question

A potentiometer wire of Length 10 m is connected in series with a battery. The e.m.f. of a cell balances against 250 cm Length of wire. If length of potentiometer wire is increased by 1 m, the new balancing length of wire will be ____________.

Options

• 2.00 m

• 2.25 m

• 2.50 m

• 2.75 m

Answer 1

A potentiometer wire of Length 10 m is connected in series with a battery. The e.m.f. of a cell balances against 250 cm Length of wire. If length of potentiometer wire is increased by 1 m, the new balancing length of wire will be 2.75 m.

Explanation:

EMF of cell,

`"E" = "k"l'`

`"E" = "E'"/l xx l'`

`"E" = "E'"/10 xx 2.5`     .....(i)

After increasing the length by 1 m,

`"E" = ("E'")/11 xx "x"`

Substituting for E from equation (i)

`"E'"/10 xx 2.5 = "E'"/11 xx "x"`

`therefore "x" = 2.5 xx 11/10 = 2.75  "m"`