# What is the Balancing Length for Its Terminal Potential Difference When Shunted with Resistance R - Physics

MCQ

In potentiometer experiment, if l1 is the balancing length for e.m.f. of cell of internal resistance r and l2 is the balancing length for its terminal potential difference when shunted with resistance R then :

#### Options

• l_1=l_2((R+r)/R)

• l_1=l_2((R)/(R+r))

• l_1=l_2((R)/(R-r))

• l_1=l_2((R-r)/R)

#### Solution

l_1=l_2((R+r)/R)

The internal resistance of a cell is given as

r= ((l_1-l_2)/l_2)R

→r/R=(l_1-l_2)/l_2

∴ rl_2=Rl_1-Rl_2

∴l_2(R+r)=Rl_1

∴l_1=l_2(R+r)/R

Concept: Metre Bridge
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