In a meter bridge the balancing length from the left end is found to be $25 \mathrm{~cm}$. The value of the unknown resistance is (assume, standard resistance of $1 \Omega$ is in the right gap)

• A

  $0.25 \Omega$
• Correct answer
  B

  $0.33 \Omega$
• C

  $0.20 \Omega$
• D

  $0.50 \Omega$

Solution

According to given situation, circuit diagram of meter bridge is given as
At balance condition of meter bridge, $\frac{S}{R}=\frac{25}{(100-25)} \Rightarrow \frac{S}{1}=\frac{25}{75} \Rightarrow S=\frac{1}{3} \Omega=0.33 \Omega$

Hence, the correct answer is option: 'B'.