Class 12 NEET Physics Current Electricity Questions Part 1

Terminal potential difference is 2.2 V when circuit is open.
∴ e.m.f. of the cell =E=2.2 volt
Now, when the cell is connected to the externa resistance, circuit current I is given by
I=

E

R+r

=

2.2

5+r

ampere, where r is the internresistance of the cell.
Potential difference across the cell =IR
=

2.2

5+r

×5=1.8
∴5+r=

11

1.8

∴ r=

11

1.8

−5 =

110−90

18

=

10

9

Ω