Question

A cell when balanced with potentiometer gave a balance length of $50cm$. $4.5\Omega$ external resistance is introduced in the circuit, now it is balanced on $45cm$. The internal resistance of cell is

• A. $0.25\Omega$
• B. $0.5\Omega$
• C. $1.0\Omega$
• D. $1.5\Omega$

Answer 1

Answer: (B)

$0.5\Omega$

The expression of internal resistance is $r=R(\frac{l_1}{l_2}-1)=4.5(\frac{50}{45}-1)=0.5\Omega$