Applied Electricity Paper 2 , Nov/Dec. 2010  
Questions:   1 2 3 4 5 6   Main
General Comments

Question 6

(a) State one difference between an electric circuit and a magnetic circuit.

In fig. 10, calculate the:
(i) voltage across the parallel circuit;
(ii) current through resistor X;
(iii) value of resistor X.


The expected answers were:
(a) In an electric circuit, insulation confines current to a definite path but in the magnetic circuit there is no known insulation and therefore not all flux is confined to one path.
In the electric circuit, resistance is almost constant apart from changes due to temperature but in the magnetic circuit reluctance varies over a wide range due to changes in permeability.
(b)(i) 8 x 2.5 = 20V
(ii)3 - 2.5 = O.5A
(iii )Resistor X 20 /0.5
The question was on Direct Current Circuit Theory. The question was surprisingly unpopular. The performance was poor. Many candidates could not state the difference between electric and magnetic circuits. Many of them that attempted the part (b) could not also show a good understanding of KCl, characteristics of a parallel
circuit and Ohm's law.

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