Question
A secondary cell after long use has an emf of 1.9 V and a large internal resistance of 380 Ω. What maximum current can be drawn from the cell? Could the cell drive the starting motor of a car?
Solution
Given,
Emf of secondary cell,
Internal resitance of the secondary cell, r = 380
Maximum current drawn from the cell is given by,
Imax = 0.005 A
The amount of current drawn from the cell is enormously low and, this amount of current cannot drive the starting motor of a car. The current required to start the motor is a minimum of 100 A.
