Question

The length of a wire of a potentiometer is 100 cm, and the e.m.f of its standard cell is E volt. It is employed to measure the e.m.f of a battery whose internal resistance is 0.5 `Omega` If the balance point is obtained at `l`= 30 cm from the positive end, the e.m.f of the battery is ____________.

where 'i' is the current in the potentiometer

विकल्प

• `(30"E")/100`

• `(30"E")/100.5`

• `(30"E")/((100 - 0.5))`

• `(30("E" - 0.5"i"))/100`

Answer 1

The length of a wire of a potentiometer is 100 cm, and the e.m.f of its standard cell is E volt. It is employed to measure the e.m.f of a battery whose internal resistance is 0.5 `Omega` If the balance point is obtained at `l`= 30 cm from the positive end, the e.m.f of the battery is `(30"E")/100`.

Explanation:

From the principle of potentiometer, `"V" prop l`

`Rightarrow "V"/"E" = l/"L"; "where V" = "e.m.f of battery,"`

E = e.m.f of standard cell, L = Length of potentiometer wire

`therefore "V" =("E"l)/"L" = (30 "E")/100`