Question

In a given potentiometer ratio of balancing length $l$ when switch s is off to when switch is closed is 3 : 2 then r is

• A. $1\Omega$
• B. $2\Omega$
• C. $3\Omega$
• D. $4\Omega$

Answer 1

The correct option is D $4\Omega$

When S is open $\Rightarrow 5=I\lambda \times 3l$ ....(1)
When S is closed $\Rightarrow 5-ir=8i=I\lambda \times 2l$
Solving (1) & (2) $r=4\Omega$