Question

The internal resistance of cell using potentiometer is a. r = R (l1-l2) (b) r = R ( l1+l2) (C) r = R (l1-l2)/l2 (d) R = r (l1/l2)​

Answer 1

Correct option is

A

l

1

=l

2

(

R

R+r

)

The internal resistance of a cell is given as r=(

l

2

l

1

−l

2

)R

R

r

=

l

2

l

1

−l

2

∴rl

2

=Rl

1

−Rl

2

∴l

2

(R+r)=Rl

1

l

1

=l

2

(

R

R+r

)