Question

a cell of emf 1.1 V and internal resistance r is connected across an external resister of resistance R=10r. The potential difference across the resister is:
(a) 0.1 V
(b) 0.9 V
(c) 1.0 V
(d) 1.1 V​

Answer 1

Explanation:

Here the terminal voltage , V=E−ir...(1) and the current i=E/(R+r)

Now, V=E−

(R+r)

E

r=

R+r

ER

=

(1+r/R)

E

=...(2)

According to equation (1) and (2), the graph V vs i and V vs R will be as shown in figure.

As i=E/(R+r) so 1=E/(4+r) or E=4+r...(3) and

0.5=E/(9+r) or 2E=9+r....(4)

using (3), 2(4+r)=9+r or r=1Ω

Thus, E

0.9