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JAMB Physics 2012 Paper

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Question : 32

Total: 42

A newly charged 12V accumulator can easily start a car whereas eight new dry cells in series with a effective e.m.f. of 12V cannot start the same car because

The current capacity is high
The current capacity is low
it cannot be re-charged
it cannot easily be connected to a car

Solution:

Concept:

Starting a car requires a very large current, which depends on low internal resistance and high current capacity.

Explanation:

Both the accumulator and the eight dry cells have the same effective e.m.f. of

12\ \mathrm{V}

.

The accumulator has very low internal resistance, so it can supply the large current needed to turn the starter motor.

Dry cells have high internal resistance and a low current capacity, so they cannot deliver the large starting current even though their e.m.f. is

12\ \mathrm{V}

.

Answer:

The current capacity is low.

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