50)
Combining the last three equations
1
2
 
 
 
 
I
I
I
=
+
    =
+
=
+


+


ε
ε
ε
ε
1
1
2
2
1
1
2
2
1
2
1
1
–
–
–
rV
rV
r
r
V
r
r
(3 51)
Hence, V is given by,
1 2
2 1
1 2
1
2
1
2
–
r
r
r r
V
I
r
r
r
r
ε
+ε
=
+
+
(3 52)
If we want to replace the combination by a single cell, between B1 and
B2, of emf eeq and internal resistance req, we would have
V = eeq – I req
(3 53)
The last two equations should be the same and hence
1 2
2 1
1
2
eq
r
r
r
r
ε
ε
ε
+
=
+
(3