Question

A torch bulb when connected to a dry cell of e.m.f. 1.5 V draws a current of 1.5 A. If the terminal voltage is 1.2 V calculate the internal resistance of the dry cell.

Answer 1

Answer:

emf =I(R+r) or

emf=E+ir

as given in the question emf is 1.5 V and terminal voltage is 1.2 V

by putting the values on above formula

we get

1.5=1.2+ ir

i = 1.5 A

now putting this value above

We get

1.5 = 1.2+1.5r

0.3 = 1.5r

r=0.2 ohm