Alternating Current · Physics · COMEDK

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MCQ (Single Correct Answer)

1
A power transmission line feeds input power at 2200 V to a step-down transformer with its primary windings having 2000 turns. The output power is delivered at 220 V by the transformer. If the current in the primary of the transformer is 2 A and its efficiency is $80 \%$, the output current would be:
COMEDK 2025 Evening Shift
2
A series LCR circuit having $\mathrm{R}=44 \Omega, \mathrm{~L}=2 \mathrm{H}$ and $\mathrm{C}=25 \mu \mathrm{~F}$ is connected to a variable frequency of 220 V . What is the average power transferred to the circuit in one complete cycle if the frequency of supply equals the natural frequency of the circuit?
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3
In a pure inductive circuit, a sinusoidal voltage $V(t)=200 \sin 250 t$ is applied to a pure inductance of $\mathrm{L}=0.02 \mathrm{H}$. The current through the coil is:
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4
The instantaneous values of alternating current and voltages in a circuit are $\mathrm{I}=\frac{3}{\sqrt{2}} \sin (200 \pi t)$ ampere and $\mathrm{V}=\frac{3}{\sqrt{2}} \sin \left(200 \pi t+\frac{\pi}{6}\right)$ volt. What is the average power consumed in the circuit in watt ?
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5
The ratio of the number of turns of the primary coil to the secondary coil of an ideal transformer is $5: 1$. The primary is connected to 220 V supply. What is the output power of the transformer if the output resistance is $11 \Omega$ ?
COMEDK 2025 Afternoon Shift
6
In which of the following circuit do we find the current and voltage in phase?
COMEDK 2025 Afternoon Shift
7
What should be the value of the inductance of the coil which is to be connected to 220 V , 50 Hz supply so that maximum current of $3 \sqrt{2} A$ flows through the circuit ?
COMEDK 2025 Afternoon Shift
8
An ideal inductor is connected across a capacitor. Oscillations of energy $K$ are set up in the circuit. The capacitor plates are slowly drawn apart such that the frequency of oscillations is quadrupled. The work done in the process is
COMEDK 2025 Morning Shift
9
If $R$ and $L$ denote resistance and inductance of a material, then the dimension of $L R$ will be:
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10
A bulb of resistance 280 Ohm is supplied with a voltage $\mathrm{V}=400 \sin \pi \mathrm{t}$. The peak current is
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11
An LCR series ac circuit is at resonance with 10 V each across $\mathrm{L}, \mathrm{C}$ and R . If the resistance is halved, the respective voltage across $R, C$ and $L$ are
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12

When an A.C. source is connected to a inductive circuit,

COMEDK 2024 Evening Shift
13

In the $$\mathrm{A} . \mathrm{C}$$. circuit given below, voltmeters $$\mathrm{V}_1$$ and $$\mathrm{V}_2$$ read $$100 \mathrm{~V}$$ each. Find the reading of the voltmeter $$\mathrm{V}_3$$ and the ammeter $$\mathrm{A}$$.

COMEDK 2024 Evening Shift Physics - Alternating Current Question 12 English

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14

A transformer has 400 turns in its primary winding and 800 turns in its secondary winding. The primary voltage is $$20 \mathrm{~V}$$ and the load in the secondary is 4 ohm. The current in the primary, assuming it to be an ideal transformer, is

COMEDK 2024 Afternoon Shift
15

A group of devices having a total power rating of 500 watt is supplied by an $$\mathrm{AC}$$ voltage $$E=200 \sin \left(3.14 t+\frac{\pi}{4}\right)$$. Then the r.m.s. value of the circuit current is

COMEDK 2024 Afternoon Shift
16

An AC voltage source of variable angular frequency $$\omega$$ and fixed amplitude $$\mathrm{V}_0$$ is connected in series with a capacitance $$\mathrm{C}$$ and an electric bulb of resistance $$\mathrm{R}$$ (inductance zero). When $$\omega$$ is decreased

COMEDK 2024 Afternoon Shift
17

A transformer which steps down $$330 \mathrm{~V}$$ to $$33 \mathrm{~V}$$ is to operate a device having impedance $$110 \Omega$$. The current drawn by the primary coil of the transformer is :

COMEDK 2024 Morning Shift
18

A coil of inductance $$1 \mathrm{H}$$ and resistance $$100 \Omega$$ is connected to an alternating current source of frequency $$\frac{50}{\pi} \mathrm{~Hz}$$. What will be the phase difference between the current and voltage?

COMEDK 2024 Morning Shift
19

A coil offers a resistance of $$20 \mathrm{~ohm}$$ for a direct current. If we send an alternating current through the same coil, the resistance offered by the coil to the alternating current will be :

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20

The capacitance of a parallel plate capacitor is $$400 \mathrm{~pF}$$. It is connected to an ac source of $$100 \mathrm{~V}$$ having an angular frequency $$100 \mathrm{~rad~s}^{-1}$$. If the rms value of the current is $$4 \mu \mathrm{A}$$, the displacement current is:

COMEDK 2024 Morning Shift
21

The instantaneous values of alternating current and voltages in a circuit given as

$$\begin{aligned} & i=\frac{1}{\sqrt{2}} \sin (100 \pi t) \mathrm{amp} \\ & e=\frac{1}{\sqrt{2}} \sin (100 \pi t+\pi / 3) \text { volt } \end{aligned}$$

The average power (in watts) consumed in the circuit is

COMEDK 2023 Morning Shift
22

In the series L-C-R circuit shown, the impedance is

COMEDK 2023 Morning Shift Physics - Alternating Current Question 24 English

COMEDK 2023 Morning Shift
23

In the case of an inductor

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24

In an electrical circuit $$R, L, C$$ and $$\mathrm{AC}$$ voltage source are all connected in series. When $$L$$ is removed from the circuit, the phase difference between the voltage and the current in the circuit is $$\pi / 3$$. If instead $$C$$ is removed from the circuit, the phase difference is again $$\pi / 3$$. The power factor of the circuit is

COMEDK 2023 Morning Shift
25

$$220 \mathrm{~V}$$ ac is more dangerous than $$220 \mathrm{~V}$$ dc Why?

COMEDK 2023 Evening Shift
26

What should be the inductance of an inductor connected to $$200 \mathrm{~V}, 50 \mathrm{~Hz}$$ source so that the maximum current of $$\sqrt{2}$$ A flows through it?

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27

During the phenomenon of resonance

COMEDK 2022
28

A DC ammeter and a hot wire ammeter are connected to a circuit in series. When a direct current is passed through circuit, the DC ammeter shows 6 A. When AC current flows through circuit, what is the average readings in DC ammeter and the AC ammeter, if DC and AC currents flows simultaneously through the circuit?

COMEDK 2022
29

A series L-C-R circuit is connected to an AC source of 220 V and 50 Hz shown in figure. If the readings of the three voltmeters $$V_1,V_2$$ and $$V_3$$ are 65 V, 415 V and 204 V respectively, the value of inductance and capacitance will be

COMEDK 2022 Physics - Alternating Current Question 27 English

COMEDK 2022
30

An alternating voltage = 200 $$\sin 100t$$ is applied to a series combination of $$R=30\Omega$$ and an inductor of 400 mH. The power factor of the circuit is,

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31

The AC voltage across a resistance can be measured using a

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32

The formula of capacitative reactance is

COMEDK 2021
33

For the same resonant frequency, if L is changed from L to $${L \over 3}$$, then capacitance should change from C to

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34

What should be the value of self-inductance of an inductor that should be connected to 220 V 50 Hz supply, so that a maximum current of 0.9 A flows through it?

COMEDK 2021
35

If impedance is $$\sqrt3$$ times of resistance, then find phase difference.

COMEDK 2021
36

For a series L-C-R circuit at resonance, which statement is not true?

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