Physics (Essay) Paper 2 WASSCE (PC 2ND), 2020

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.

 

H5

         

 

H6