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CBSE

#1 Class 12 Physics Alternating Current 2021 Short 2M

Explain briefly how the brightness of a bulb changes when (1) the number of turns of the inductor in series is reduced, and (2) a capacitor of reactance $X_C = X_L$ is included in the circuit.

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CBSE

#2 Class 12 Physics Alternating Current 2020 Short 1M

Define capacitive reactance. Write its SI unit.

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CBSE

#3 Class 12 Physics Alternating Current 2019 Short 1M

What is the function of a step-up transformer?

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CBSE

#4 Class 12 Physics Alternating Current 2018 Short 1M

What is inductive reactance? Write its SI unit and formula.

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CBSE

#5 Class 12 Physics Alternating Current 2020 Mcq 1M

Which of the following graphs represents the variation of current $I$ with frequency $f$ in an AC circuit containing a pure capacitor?

A. I increases with f

B. I decreases with f

C. I is constant with f

D. I first increases then decreases

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CBSE

#6 Class 12 Physics Alternating Current 2021 Mcq 1M

Which among the following is NOT a cause for power loss in a transformer?

A. Eddy currents in the soft iron core

B. Magnetic flux leakage between primary and secondary coils

C. Humming sound due to magnetostriction

D. Primary coil made of very thick copper wire

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CBSE

#7 Class 12 Physics Alternating Current 2022 Mcq 1M

A series LCR circuit is shown. The source frequency $f$ is varied but current is kept unchanged. Which curve shows the changes of $V_C$ and $V_L$ with frequency?

A. Curve A

B. Curve B

C. Curve C

D. Curve D

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CBSE

#8 Class 12 Physics Alternating Current 2016 Mcq 1M

The best material for the core of a transformer is

A. soft iron

B. mild steel

C. hard steel

D. stainless steel

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CBSE

#9 Class 12 Physics Alternating Current 2020 Mcq 1M

In a transformer, the output current and voltage are 4 A and 20 V respectively. If the ratio of primary to secondary turns is 2:1, what are the input current and voltage?

A. 1 A and 20 V

B. 2 A and 40 V

C. 4 A and 80 V

D. 8 A and 160 V

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#10 Class 12 Physics Alternating Current 2021 Mcq 1M

In an AC circuit, voltage applied is $V = 100\sin(t)$. If impedance of the circuit is 110 $\Omega$ and phase difference between current and voltage is 60°, the power in the circuit is

A. 55 W

B. 110 W

C. 220 W

D. 330 W

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CBSE

#11 Class 12 Physics Alternating Current 2019 Mcq 1M

For an AC circuit, average power is 60 W. What will be the power factor if its apparent power is 100 W?

A. 0.6

B. 1.6

C. 2.4

D. 3.2

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CBSE

#12 Class 12 Physics Alternating Current 2020 Short 1M

Write the expression for the quality factor (Q-factor) of an LCR series circuit having resistance $R$ and inductance $L$ at resonance angular frequency $\omega_0$.

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#13 Class 12 Physics Alternating Current 2022 Mcq 1M

In an LCR series circuit, inductive reactance = 50 $\Omega$, capacitive reactance = 35 $\Omega$, resistance = 20 $\Omega$. The impedance of the circuit is

A. 15 $\Omega$

B. 25 $\Omega$

C. 35 $\Omega$

D. 45 $\Omega$

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CBSE

#14 Class 12 Physics Alternating Current 2019 Mcq 1M

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

A. zero

B. 50 V

C. $50\sqrt{2}$ V

D. 100 V

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CBSE

#15 Class 12 Physics Alternating Current 2021 Mcq 1M

Reactance of a capacitor of capacitance $C$ for an alternating current of frequency $\frac{400}{\pi}$ Hz is 25 $\Omega$. The value of $C$ is

A. 25 $\mu$F

B. 50 $\mu$F

C. 75 $\mu$F

D. 100 $\mu$F

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CBSE

#16 Class 12 Physics Alternating Current 2020 Mcq 1M

The value of current flowing through an inductor of inductance 1 H with negligible resistance when connected to an AC source of 200 V and 50 Hz is

A. 0.64 A

B. 1.64 A

C. 2.64 A

D. 3.64 A

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CBSE

#17 Class 12 Physics Alternating Current 2018 Mcq 1M

In an AC circuit containing only a capacitor, the current

A. leads the voltage by 90°

B. leads the voltage by 180°

C. lags behind the voltage by 90°

D. remains in phase with the voltage

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#18 Class 12 Physics Alternating Current 2019 Mcq 1M

In a circuit, the current lags behind the voltage by a phase difference of $\pi/2$ radians. The circuit contains

A. only R

B. only L

C. only C

D. R and C

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CBSE

#19 Class 12 Physics Alternating Current 2021 Mcq 1M

The peak voltage of an AC source is 440 V. Its virtual (rms) voltage is

A. 220 V

B. 440 V

C. $220\sqrt{2}$ V

D. $440\sqrt{2}$ V

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#20 Class 12 Physics Alternating Current 2020 Short 1M

What is the ratio of peak value to rms value of AC?

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