Question

In meter bridge the balancing length from left and when standard resistance of 1 Ω is in right gas is found to be 20 cm. The value of unknown resistance is

• A. 0.25 Ω
• B. 0.4 Ω
• C. 0.5 Ω
• D. 4 Ω

Answer 1

Answer: (A)

0.25 Ω

Answer 2

The condition of wheatstone bridge gives $\frac { X } { R } = \frac { 20 r } { 80 r }$

r- resistance of wire per cm, X- unknown resistance

∴ $X = \frac { 20 } { 80 } \times R = \frac { 1 } { 4 } \times 1 = 0.25 \Omega$