In a circuit consisting of a capacitance and a generator with alternating emf $\mathrm{E}_{\mathrm{g}}=\mathrm{E}_{\mathrm{g}_{0}} \sin \omega \mathrm{t}, \mathrm{V}_{\mathrm{C}}$ and $\mathrm{I}_{\mathrm{C}}$ are the voltage and current. Correct phase diagram for such circuit is :

JEE Main · 2021 · 22 Jul 2021 · Shift 2 · Alternating Current

In a circuit consisting of a capacitance and a generator with alternating emf

E_{g} = E_{g_{0}} sin ω t, V_{C}

and

I_{C}

are the voltage and current. Correct phase diagram for such circuit is :

Answer: (B)

For a pure capacitance the charge follows the voltage,

q = C V_{C}

with

V_{C} = E_{g 0} sin ω t

, so

I_{C} = \frac{d q}{d t} = ω C E_{g 0} cos ω t = ω C E_{g 0} sin (ω t + \frac{π}{2})

The current reaches its peak a quarter cycle earlier than the voltage, so in the rotating phasor picture the voltage phasor sits at angle

ω t

from the reference axis and the current phasor stands a further

9 0^{\circ}

ahead of it, both turning anticlockwise.

JEE Main · 2021 · 22 Jul 2021 · Shift 2 · Single correct option