In a potentiometer circuit, a cell of 1.5 V EMF gives balance point at 30 cm length of wire. If another cell of 2.5 V EMF replaces the first cell, then at what length of the wire will the balance point occur?

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HPCL Engineer Electrical 01 Nov 2022 Official Paper
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  1. 50 cm
  2. 30 cm
  3. 60 cm
  4. 40 cm

Answer (Detailed Solution Below)

Option 1 : 50 cm
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Detailed Solution

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The correct answer is option 1):(50 cm)

Concept:

As we know in a potentiometer EMF has two cells in which ℓ1 and ℓ2 be the null points and E1 and E2 be the EMFs, therefore we can write it as,

\(\frac{{{E_1}}}{{{E_2}}} = \frac{{{\ell_1}}}{{{\ell_2}}}\)

Calculation:

Given:

E= 1.5 V

E2 = 2.5 V

l1 = 30 cm

l2 = ?

Using\(\frac{{{E_1}}}{{{E_2}}} = \frac{{{\ell_1}}}{{{\ell_2}}}\)

we get;

l2 = l× \(E_2 \over E_1\)

= 30 × \(2.5 \over 1.5\)

= 50 cm

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