Applied Electricity Paper 2 , May/June 2010
 Questions: 1 2 3 4 5 6 7 8 Main
Weakness/Remedies
Strength

Question 2

(a) (i) Define the term impedance.
(ii) List two impedance components.
(b) A 220 V, 50 Hz supply is connected across a series circuit of 15 n resistance and 20 n reactance. Calculate the:
(i) impedance;
(ii) current.

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Observation

The expected answers were as follows:
(a) (i) Impedance of any a.c. circuit is the ratio of the applied voltage to the current.
OR
Impedance is the property of a material to oppose an a.c. current.
(ii)      Any two of the components
Resistor
Inductor

Capacitor

ii)

L = e~V,50HZ

= 250

(ii) V/Z=220/25=8.8 A

The question was on Alternating Current Circuit Theory. Many of the candidates did this correctly, except for the very few who had difficulty understanding the basics.
'OPPosition of current in an alternating current circuit' was either absent or poorly presented in their responses to the definition of impedance.
Some candidates had problems in computing the circuit impedance.