Question

Please tell the 5th question.

Answer 1

I=1A

R=1.9Ω

e=I(R+r)

=1(1.9+r)

=1.9+r                       [1]

2nd case

e=0.5(3.9+r)

 = 1.95+0.5r        [2]

from 1 and 2

1.9+r=1.95+0.5r

r=0.05/0.5

r=0.1 Ohms

e=1.9+0.1

=2V