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Electronics Paper 2, Nov/Dec. 2010  
Questions: 1 2 3 4 5 6 7 8 9 10 Main
General Comments
Weakness/Remedies
Strength















Question 2

Figure 5 is a resistive circuit.

From figure 5, calculate the
(a) effective resistance of the circuit;
(b) voltage across the 30 0 resistor;
(c) voltage (V) applied to the circuit;
(d) power dissipated in the 100 resistor.

_____________________________________________________________________________________________________
OBSERVATION

The expected answers were:
(a) R / /branch = 30x20Ω = 30x20Ω  = 120
                             30+20        50
Effective resistance= 10 + 20 + 120 = 42Ω
(b) Current thro' 30Ω resistor 20 / 50 x 2.5A = 50 / 50 A = lA
Voltage across 30Ω resistor = 30 xlV = 30 V
VR30 = R//Branch x IT
= 12 x 2.5
= 30V
(c)Voltage applied to circuit, V = 2.5 x 42 V = 105 V
{d} PR10 = I² RlO
= 2.5 x 2.5 x 10
= 62.5 W
For Questions 2, three important theorems of circuit theory were required namely: equivalent resistance for resistors connected in parallel and in series, Ohm's law and the current divider rule.
The question was on Basic Electrical Theory. The question was popular with the candidates. Many candidates that attempted as may be expected scored full marks.

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