The charge that a fully charged 12 V car battery can supply is 100 kC. The starter motor of the car requires a current of 200 A for an average period of 2.0 s.

Question 16

The charge that a fully charged 12 V car battery can supply is 100 kC. The starter motor of the car requires a current of 200 A for an average period of 2.0 s. The battery does not recharge because of a fault.

What is the maximum number of times the starter motor of the car can be used?

A 21                 B 25                 C 42                D 250

Reference: Past Exam Paper – June 2016 Paper 12 Q35

Solution:

Answer: D.

Total charge = 100 kC = 100 000 C

The starter motor of the car requires a current of 200A for an average period of 2.0 s.

Charge Q = It

Q = 200 × 2.0 = 400 C

The starter motor requires a charge of 400 C when used for 1 time.

400 C - - > 1 time

100 000 C - - > 100 000 / 400 = 250 times