Question

Three cells of emf E are connected in series to an external resistance 10 ohms . The current through the external resistor is i . When the same cell are connected in parallel to the same , the current is still i . The internal resistance of each cell is ?????

Answer 1

Answer:

internal resistance r=10

Explanation:

internal resistance of each cell is r

1. cell in series

emf 3E internal resistance 3r

current i=3E/(3r+10)

2. cell in parallel

emf E interal resistance r/3

i=E/(r/3+10)

both case current is same.

3E/(3r+10)=E/(r/3+10)

2r=20

by solving this

r=10