Question

20 identical cells are connected in series with a load of resistance and current in it is ( I ) now polarity of some cell are reversed then current becomes( I/5 ) calculate no of cells reversed​

Answer 1

Explanation:

Number of cells =n

EMF of each cell =E

Internal resistance of each cell, =r

All the cells are in series.

Thus,

Total internal resistance, R=nr

Total EMF, e=nE

As the two cells are connected in reverse polarity, these two cells will cancel-out the contribution of other two cells in the loop.

Then, the net EMF across the circuit will be

E

eq

=nE−4E

The current I in the circuit =

nr

nE−4E

Voltage across the opposite connected batteries, V=E−Ir

V=E−

nr

E(n−4)

×r

V=

n

4E

Therefore, the voltage across the battery A or B will be

n

4E.