PHYSICS · Subjective · CBSE · Physics · Alternating Current · Alternating Current
Problem
A series circuit contains a resistor of 50Ω, an inductor of 200mH and a capacitor of 2μF connected to an adjustable–frequency a.c. source.
(i) Explain, without actual calculation, how the opposition offered by the inductor and the capacitor to the alternating current changes when the supply frequency is steadily increased from a very low value to a very high value.
(ii) On a single set of labelled axes, draw a qualitative (rough–sketch) curve of the magnitude of impedance Z versus frequency f for this circuit. Mark clearly the frequency at which the current is expected to attain its maximum value.
(iii) Describe how the phase angle between the source voltage and the circuit current varies over the same range of frequency and indicate its sign in the low-frequency and high-frequency limits.
(iv) State what happens to the power factor as the circuit is tuned through the frequency that you marked in part (ii) and justify your answer conceptually.