The expected answers were:
(a)
Primary cell |
Secondary cell |
-- |
(i) |
Cannot be recharged |
(i) |
Can be recharged |
|
|
once the chemicals |
|
and used many |
|
|
are exhausted. |
|
times each time the |
|
|
|
|
energy is used. |
|
(ii) |
Converts chemical |
(i i i) |
Chemical action is |
|
|
energy into electrical |
|
reversible. |
|
|
energy. |
|
|
|
(b) Vopen circuit = 9 V
Vload = 8.5 V
Iload = 1 A
(i) Vdropon load = (9 - 8.5) V = 0.5 V
Rinternal = V drop/Il = 0.5/1 = 0.50
OR
I = E/(R + r) where r = internal resistance
r = E/I-R = 9.0 - 8.5 = 0.50
(ii) Power dissipated = 12Rj
= 1²x 0.5 = 0.5W
The question was on Electrical Energy Supply and Direct Current
Circuit Theory. The question was less unpopular. The
performance was average.
Many of the candidates gave at least one difference that was
correct. However, those who did not understand the part (b) of
the question could not do this satisfactorily due to lack of practice
and exposure as reported.