Question 11
(a)(i) Define each of the following terms as applied to a.c circuits:
(I) reactance;
(II) impedance.
(ii) Sketch a graph of impedance Z, against frequency for an RLC series circuit. Indicate the point of resonance on the graph.
(iii) An inductor of inductance 100 mmH and a capacitor of capacitance 2 μF are connected in series in an a.c. circuit. Calculate the frequency at which the system resonates. [π = 3.14]
(B)Draw and label a diagram of a step-down transformer.
Observation
Part (a): Candidates performance was below average.
Part (b): Candidates performance was below average.
The expected answers are:
11. (a) (i) Definition
(I) Reactance
Opposition to the flow of alternating current by a capacitor or an inductor or both.
(II) Impedance
The total opposition to the flow of alternating current by a mixed circuit of a resistor and an inductor or capacitor or a combination of the three components.
