Answer the following questions :
(a) In any a.c. circuit, is the applied instantaneous voltage equal to the algebraic sum of the instantaneous voltages acorss the series elements of the circuit ? Is the same true for r.m.s. voltage?
(b) A capacitor is used in the primary circuit of an induction coil.
(c ) An applied voltage signal consists of a superposition of a d.c. voltage and an a.c. voltage of high frequency. The circuit consists of an inductor and a capacitor in series. Show that the d.c. signal will appear across C and the a.c. signal will appear across L.
(d) A choke coil in series with a lamp is connected to a d.c. line. The lamp is seen to shine brightly. Insertion of an iron core in the choke causes no change in the lamp's brightness. Predict the corresponding observation if the connection is to an a.c. line.
(e) Why is choke coil needed in use of fluorescent tubes with ac mains ? Why can we not use an ordinary resistor instead of choke coil?

Explanation

As we know `X_(C) = (1)/(2 pi f C) `
`X_(L) = omega L = 2 pi `f L
For DC, frequency f = 0 `therefore X_(C) = infty`
Therefore, capacitor blocks DC and hence, DC will appear across C.
For AC which is having high frequency, `X_(L) ` is very large and hence, the inductor blocks AC. Thus, AC will appear across L.