EASY

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Statement $(1) :$ An LCR circuit connected to an AC source has maximum average power at resonance.

Statement $(2) :$ A resistor only circuit with zero phase difference has maximum average power.

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Important Questions on Alternating Current

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

What is power dissipation in an a.c. circuit in which voltage and current are given by

V = 300 \sin (ω t + π / 2), I = 5 \sin ω t

MEDIUM

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

The power factor of

R - L

circuit is

\frac{1}{\sqrt{3}}

. If the inductive reactance is

2 Ω

. The value of resistance is

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

A current

I = I_{0} \sin (ω t - \frac{π}{2})

flows in an

AC

circuit, if potential

E = E_{0} \sin ω t

has been applied. The power consumption in the circuit will be

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

In an a.c. circuit containing

L, C, R

in series, the ratio of true power to apparent power is (

Z =

impedance of the circuit,

R =

resistance,

ϕ =

phase difference between the r.m.s. values of current and e.m.f.)

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

In series LCR circuit

R = 18 Ω

and impedance is

33 Ω

. An RMS voltage of

220 V

is applied across the circuit. The true power consumed in the AC circuit is

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

A series LCR circuit is designed to resonate at an angular frequency

ω_{0} = 10^{5} rad s^{- 1} .

The circuit draws

16 W

power from

120 V

source at resonance. The value of resistance

R

in the circuit is ________

Ω .

MEDIUM

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

In an AC circuit, the current flowing is

I = 5 \sin (100 t - \frac{π}{2}) A

and the potential difference is

e = 200 \sin (100 t)

. The power consumption is equal to

HARD

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

Two circuits are shown in figure $(a)$ and $(b)$ . At a frequency of _______ $rad s^{- 1}$ the average power dissipated in one cycle will be the same in both the circuits.

Question Image

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

An alternating voltage

V = V_{0} \sin ω t

is applied across a circuit and as a result, a current

I = I_{0} \sin (ω t + \frac{π}{2})

flows in it. The power consumed per cycle is

MEDIUM

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

In an

A.C.

circuit, the instantaneous e.m.f. and current are given by,

E = 100 \sin 30 t

, I = 20 \sin (30 t - \frac{π}{4})

. In one cycle of

A.C.

, the average power consumed by the circuit (in watt) and the watt-less current (in ampere) are, respectively:

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

A sinusoidal voltage of peak value

250 V

is applied to a series

L C R

circuit, in which

R = 8 Ω, L = 24 mH

and

C = 60 μ F

. The value of power dissipated at resonant condition is

x

kW

. The value of

x

to the nearest integer is _______.

MEDIUM

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

An inductor

20 mH

, a capacitor

50 μ F

and a resistor

40 Ω

are connected in series across a source of emf

V = 10 \sin 340 t

. The power loss in

AC

circuit is:

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

In an

A C

circuit, current is

3 A

and voltage

210 V

and power is

63 W

. The power factor is

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

In the series

LCR

circuit, the power dissipation is through:

MEDIUM

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

A lamp consumes only

50 %

of maximum power in an A.C. circuit. What is the phase difference between the applied voltage and the circuit current?

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

An AC circuit has an inductor and a resistor of resistance

R

in series, such that

X_{L} = 3 R

. Now, a capacitor is added in series such that

X_{C} = 2 R

. the ratio of the new power factor with the old power factor of the circuit is

\sqrt{5} : x

. The value of

x

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

A resistor of

20 Ω

and a capacitor are connected in series with an

A C

current source of

50 Hz .

What should be the capacitance to produce a phase difference of

30 °

between the voltage and current?

EASY

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

In a series

LR

circuit, power of

400 W

is dissipated from a source of

250 V, 50 Hz

. The power factor of the circuit is

0.8

. In order to bring the power factor to unity, a capacitor of value

C

is added in series to the

L

and

R

. Taking the value of

C

(\frac{n}{3 π}) μF

, then value of

n

MEDIUM

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

The potential differences across the resistance, capacitance, and inductance are

80 V, 40 V

and

100 V

, respectively in an LCR circuit. The power factor of this circuit is

MEDIUM

Physics>Electricity and Magnetism>Alternating Current>Power in AC Circuits

An inductor

20 mH,

capacitor

100 μF

and a resistor

50 Ω

are connected in series across a source of emf,

V = 10 \sin (314 t)

. The power loss in the circuit is

Statement (1): An LCR circuit connected to an AC source has maximum average power at resonance. Statement (2): A resistor only circuit with zero phase difference has maximum average power.

Important Questions on Alternating Current

Learn and Prepare for any exam you want !

Statement $(1) :$ An LCR circuit connected to an AC source has maximum average power at resonance.

Statement $(2) :$ A resistor only circuit with zero phase difference has maximum average power.