- #1

- 92

- 0

B)) A variable capacitor "added" in this circuit maybe adjusted until the lamp glows with normal brilliance. Explain how this is possible

ATTEMPT:

If V is the voltage of alternating source, and I is the current flowing when no inductor or capacitor is connected, then

I 1=V/R

If now a choke of inductive reactance Xl is placed in series with the electric lamp, the new impedance of the circuit will be

Z 1=underroot<Rsquare + Xlsquare>

Therefore current flowing will be

I 2=V/[underroot<Rsquare + Xlsquare>]

From the comparison of equations of current, we see that I 2 < I 1 and that is why the electric lamp is dimmed on placing a choke in the circuit.

When a variable capacitor is added in series, Xc opposes Xl and thus

Z 2=underroot<Rsquare + (Xlsquare-Xcsquare)>

Therefore,

I 3=V/[underroot<Rsquare + (Xlsquare-Xcsquare)>]

If Xl = Xc, then Z 2=R

And current becomes equal to I 1 as if there's no reactance in the circuit and hence the lamp glows with normal brilliance.

Can you check whether this is a correct explanation?