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This mock test of Alternative Current Practice Level - 1 for Class 12 helps you for every Class 12 entrance exam.
This contains 35 Multiple Choice Questions for Class 12 Alternative Current Practice Level - 1 (mcq) to study with solutions a complete question bank.
The solved questions answers in this Alternative Current Practice Level - 1 quiz give you a good mix of easy questions and tough questions. Class 12
students definitely take this Alternative Current Practice Level - 1 exercise for a better result in the exam. You can find other Alternative Current Practice Level - 1 extra questions,
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QUESTION: 1

A capacitor in an LC oscillator has a maximum potential difference of 17 V and a maximum energy of 160 μJ. When the capacitor has a potential difference of 5 V and an energy of 10μJ, what is the energy stored in the magnetic field ?

Solution:

QUESTION: 2

If we increase the driving frequency in a circuit with apurely resistive load, then amplitude VR

Solution:

QUESTION: 3

The figure shows a sine curve S(t) = sinωt and three other sinusoidal curves A(t), B(t) and C(t), each of the form sin (ωt - ). Which curve is according to the most negative value off.

Solution:

QUESTION: 4

A parallel-plate capacitor with rectangular plates is being discharged. A rectangular loop, centered on the plates and between them, measures L by 2L : the plates measure 2L by 4L. The fraction of the displacement current is encircled by the loop if that current is uniform

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QUESTION: 5

Figure shows three oscillating LC circuit with identical inductors and capacitors. If t_{1}, t_{2}, t_{3} are the time taken by the circuits I, II, III for fully discharge, then

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QUESTION: 6

In an oscillating LC circuit with L = 50 mH and C = 4.0 μF, the current is initially a maximum. How long will it take before the capacitor is fully discharged for the first time :

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QUESTION: 7

Charges on the capacitors in three oscillating LC circuits vary as follows (1) q = 2 cos 4t. (2) q = 4cos t, (3) q = 3 cos 4t, (4) q = 4 cos 2t, with q in coulomb and t in second. In which circuit (s) current amplitude is greatest:

Solution:

QUESTION: 8

A charged capacitor and an inductor are connected in series at time t = 0. Read the statements :

(1) the charge on the capacitor is zero after a time T/2

(2) The charge on the capacitor is zero after time T/4

(3) the energy stored in the capacitor maximum at T/2

(4) the energy stored in the inductor is maximum at T/4

Solution:

QUESTION: 9

If we increase the driving frequency in a circuit with a purely capacitive load. Read the following statements

(1) amplitude V_{c }increases

(2) amplitude V_{c} decrease

(3) amplitude i_{c} increase

(4) amplitude i_{c} decreases

Out of these, the correct statement(s) is/are

Solution:

QUESTION: 10

If we increase the deriving frequency in a circuit with a purely inductive load. Read the following statements :

(1) amplitude V_{L} remain constant

(2) amplitude V_{L} increases

(3) amplitude i_{L} increases

(4) amplitude i_{L} decreases

Out of these, the correct statement (s) is / are

Solution:

QUESTION: 11

Here are the capacitive reactance and inductive reactance, respectively, for three sinusoidally driven

RLC circuits : (1) 50 W, 100 W (2) 100 W, 50 W (3) 100 W,100 W

Which is in resonance ?

Solution:

QUESTION: 12

An alternating current emf device has a smaller resistance than that of the resistive load, to increase the transfer of energy from the device to the load, a transformer will be connected between two. Then

Solution:

QUESTION: 13

The figure here gives the electric field of an electromagnetic wave at a certain point and a certain instant. The wave is transporting energy in the negative z-direction. The direction of the magnetic field of the wave at that point and instant is :

Solution:

QUESTION: 14

Which of the following plots may represent the eactance of a series LC combination ?

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QUESTION: 15

An AC source is rated 220 V, 50 Hz. The average voltage is calculated in a time interval of 0.01s. It

Solution:

QUESTION: 16

An electromagnetic wave going through vacum is described by E = E_{0} sin (kx-ωt) ; B = B_{0} sin (kx-ωt) .

Then

Solution:

QUESTION: 17

Alternating current can not be measured by dc ammeterbecause

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QUESTION: 18

If a current I given by I_{0 } flows in an ac circuit across which an ac potential of V = V_{0} sinωt has been applied, then the power consumption P in the circuit will be

Solution:

QUESTION: 19

An alternating voltage V = 200√2 sin(100t) is connected to a 1 microfarad capacitor through an ac ammeter. The reading of the ammeter shall be

Solution:

QUESTION: 20

A 220 V, 50 Hz ac source is connected to an inductance of 0.2 H and a resistance of 20 ohm in series. What is the current in the circuit?

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QUESTION: 21

In the circuit shown below, the ac source has voltage V = 20 cos(ωt ) volt with ω = 2000 rad/s. the amplitude of the current will be nearest to

Solution:

QUESTION: 22

The power factor of an ac circuit having resistance (R) and inductance (L) connected in series and an angular velocity ω is

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QUESTION: 23

An inductor of inductance L and resistor of resistance R are joined in series and connected by a source of frequency ω . Power dissipated in the circuit is

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QUESTION: 24

In a LCR circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the nductance should be change from L to

Solution:

QUESTION: 25

In an LCR series ac circuit, the voltage across each of the components, L, C and R is 50 V. The voltage across the LC combination will be

Solution:

QUESTION: 26

A bulb and a capacitor are connected in series to a source of alternating current. If its frequency is increased, while keeping the voltage of the source constant, then

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QUESTION: 27

An alternating e.m.f. of angular frequency ω is applied across an inductance. The instantaneous power developed in the circuit has an angular frequency

Solution:

QUESTION: 28

The diagram shows a capacitor C and a resistor R connected in series to an ac source. V_{1} and V_{2} are voltmeters and A is an ammeter.

Consider now the following statements

I. Readings in A and V_{2} are always in phase

II. Reading in V_{1} is ahead in phase with reading in V_{2}

III. Readings in A and V_{1} are always in phass.

Which of these statements are/is correct?

Solution:

QUESTION: 29

The voltage of an ac supply varies with time (t) as V = 120 sin100πtcos100 πt . The maximum voltage and frequency respectively are

Solution:

QUESTION: 30

Match the following

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QUESTION: 31

An ac source of angular frequency ω is fed across a resistor r and a capacitor C in series. The current registered is I. If now the frequency of source is changed to ω / 3 (but maintaining the same voltage), the current in the circuit is found to be halved. Calculate the ratio of reactance to resistance at the original frequency ω

Solution:

QUESTION: 32

The output current versus time curve of a rectifier is shown in the figure. The average value of output current in this case is

Solution:

QUESTION: 33

When an ac source of e.m.f. e = V_{0} sin(100t) is connected across a circuit, the phase difference between the e.m.f. e and the current i in the circuit is observed to be π / 4, as shown in the diagram If the circuit consists possibly only of RC or LC in series, find the relationship between the two elements

Solution:

QUESTION: 34

In an oscillatory circuit, L = 0.4 H, C = 0.0024 μF. Themaximum value of the resistance that should be included is:

Solution:

QUESTION: 35

At t < 0, the capacitor is charged and the switch is opened. At t = 0 the switch is closed. The shortest time T at which the charge on the capacitor will be zero is given by :

Solution:

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