Question 390: AC fundamentals

Question

A capacitor, an inductor and an electric bulb are connected in series to an a.c. supply of variable frequency. As the frequency of the supply is increased gradually, then the electric bulb is found to

Accepted Answer

The given circuit acts like a series LCR circuit.
$$I=\frac{V}{Z}=\frac{V}{\sqrt{R_2+\left(\omega L-\frac{1}{\omega C}\right)^2}}$$
From the above formula, when $$\omega=0$$, $$\mathrm{I}=$$ maximum
When $$\omega$$ is increased, I starts to decrease and when $$\omega=\frac{1}{\sqrt{\mathrm{LC}}}$$ the current will be zero. This cycle will repeat going forward. So brightness will increase, reach a maximum and then decrease.

Answer

increase in brightness.

Answer

decrease in brightness.

Answer

increase, reach a maximum and then decrease in brightness.

Answer

show no change in brightness.

AC fundamentals

A capacitor, an inductor and an electric bulb are connected in series to an a.c. supply of variable frequency. As the frequency of the supply is increased gradually, then the electric bulb is found to

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