Question

3. A capacitor of capacitance 30 μF is connected to an ac source of voltage V = 150 Sin 314t. Calculate the capacitive reactance and the current in the circuit.

Answer 1

Given : C=15×10

−6

F

Rms value of voltage V

rms

=220 V

Frequency of source f=50 Hz

Capacitive reactance X

C

=

2πfC

1

=

2π×50×15×10

−6

1

=212.3Ω

Rms value of current I

rms

=

X

C

V

rms

=

212.3

220

=1.04 A

Peak value of current I

o

=

2

I

rms

=

2

×1.04=1.465 A

Since X

C

∝

f

1

So capacitive reactance gets halved if the frequency is doubled.

Also, I

rms

∝

X

C

1

∝f

Socurrent becomes doubled if the frequency is doubled