Question

In the following circuit the potential difference between the points B and C is balanced against 40 cm length of potentiometer wire. In order to balance the potential difference between the points C and D, where should jockey be pressed

• A. 32 cm
• B. 16 cm
• C. 8 cm
• D. 4 cm

Answer 1

Answer: (A)

32 cm

Answer 2

$\frac { 1 } { R } = \frac { 1 } { 10 } + \frac { 1 } { 10 } = \frac { 2 } { 10 } = \frac { 1 } { 5 }$ or R₁ = 5 Ω

R₂ = 4Ω, l₁ = 40 cm, l₂ = ?

$l _ { 2 } = l _ { 1 } \frac { R _ { 2 } } { R _ { 1 } }$ or $l _ { 2 } = \frac { 40 \times 4 } { 5 } = 32 \mathrm {~cm}$