JEE Advance - Physics (2010 - Paper 1 Offline - No. 13)
An AC voltage source of variable angular frequency $$\omega$$ and fixed amplitude V0 is connected in series with a capacitance C and an electric bulb of resistance R (inductance zero). When $$\omega$$ is increased
the bulb glows dimmer.
the bulb glows brighter.
total impedance of the circuit is unchanged.
total impedance of the circuit increases.
Giải thích
Impedance of the circuit,
$$Z = \sqrt {{{({X_C})}^2} + {{(R)}^2}} = \sqrt {{{\left( {{1 \over {\omega C}}} \right)}^2} + {R^2}} $$
As $$\omega$$ increases, Z decreases.
Current in the circuit, $$I = {{{V_0}} \over Z}$$
When $$\omega$$ is increased, the impedance of the circuit decreases and the current through the bulb increases. Therefore the bulb glows brighter.