Are these practice questions for Alternating Current based on the CBSE pattern?

Yes. Every practice question is modeled on the CBSE Class 12 - Science Physics exam pattern — including MCQs, assertion-reason questions, and short-answer formats that frequently appear in CBSE papers.

Are the practice questions for Alternating Current free?

Yes. Every chapter includes free practice questions for Class 12 - Science students to get you started.

What types of questions are included?

The practice set for Alternating Current mainly includes MCQs and CBSE-style short-answer questions, with instant feedback on each answer. For full-length textbook practice, use the NCERT Solutions page.

Are the practice questions suitable for board exam preparation?

Yes. The questions test the same concepts and depth that CBSE asks in board exams. After finishing, also solve the NCERT and NCERT Exemplar exercises for Alternating Current for full coverage.

How many practice questions are there for Alternating Current?

The number scales with chapter length and concept density. Each chapter typically has 15-50 practice questions across MCQ and short-answer formats.

Alternating Current Class 12 Physics Practice Questions with Answers

easy

An ideal step-down transformer is used to power a

12

V lamp from a

240

V mains supply. If the lamp draws a current of

2

A, calculate the current drawn from the mains. Assume the transformer is 100% efficient.

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easy

Examine the main reason why alternating current (AC) is preferred over direct current (DC) for the large-scale transmission of electrical energy.

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easy

Evaluate the necessity of using a laminated iron core in a transformer instead of a solid iron core.

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easy

Define alternating current (AC).

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easy

Define the power factor of an AC circuit.

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easy

An AC voltage source is described by the equation

v = 150 \sin(100\pi t)

. If this source is connected to a

50 \text{ } \Omega

resistor, calculate the rms value of the current flowing through the resistor.

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easy

The peak voltage of an AC supply is measured to be

340

V. Calculate its rms voltage.

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easy

Name the physical quantity that plays the role of resistance in a purely inductive AC circuit and state its SI unit.

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easy

Critique the use of the term 'wattless current'. Is the current truly 'wattless', and under what specific conditions is this term applicable?

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easy

Recall the relationship between the peak value (

i_m

) and the root mean square (rms) value (

I

) of an alternating current.

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medium

A capacitor of capacitance

100 \text{ } \mu F

is connected to an AC supply of

110

V,

60

Hz. Calculate the capacitive reactance and the peak current in the circuit.

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medium

For a series LCR circuit with

L = 2.0

H,

C = 32 \text{ } \mu F

, and

R = 10 \text{ } \Omega

, calculate the resonant frequency. Also, solve for the impedance and the rms current at the resonant frequency if the circuit is connected to a

220

V AC source.

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medium

Define wattless current.

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medium

Identify the circuit elements in which the average power consumed over a complete AC cycle is zero.

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medium

Propose a method to determine whether an unknown circuit element in a sealed box is a resistor, an inductor, or a capacitor, using only a variable frequency AC voltage source and an AC ammeter.

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medium

A student designs a step-up transformer with

N_p = 50

turns and

N_s = 500

turns. They expect a 10x voltage increase. However, upon testing, they observe significant heating in the iron core and the output voltage is lower than expected. Justify the possible reasons for these discrepancies from the ideal transformer model.

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medium

In a purely inductive circuit, the average power consumed over a complete cycle is zero. Justify this statement using both a mathematical derivation and a conceptual explanation.

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medium

Recall the formula for capacitive reactance (

X_C

) and explain how it depends on the frequency of the AC source.

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medium

A light bulb is connected in series with an inductor to an AC source. Analyze what happens to the brightness of the bulb when the frequency of the AC source is increased, and explain your reasoning.

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medium

Evaluate the claim that transmitting electrical power over long distances using low-voltage DC is more efficient than using high-voltage AC. Provide a reasoned argument to support or refute this claim.

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medium

Compare the phase relationship between voltage and current in a purely resistive, a purely inductive, and a purely capacitive AC circuit. Demonstrate these relationships using phasor diagrams.

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medium

Define impedance in a series LCR circuit and recall its formula.

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medium

Examine why the average power consumed by a pure inductor or a pure capacitor in an AC circuit over one complete cycle is zero.

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medium

Analyze how the inductive reactance (

X_L

) and capacitive reactance (

X_C

) of a circuit change with the frequency of the AC source. Contrast their behavior.

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medium

Describe what a step-down transformer does and explain the relationship between the number of turns in its primary and secondary coils.

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medium

A household AC supply is rated at

220 \text{ V}

. Explain what this value represents and calculate the peak voltage of the source.

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medium

List three types of energy losses that occur in an actual transformer.

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medium

An iron-core inductor is connected in series with a light bulb to an AC source. Justify what happens to the brightness of the bulb when the frequency of the AC source is increased. How would your answer change if the inductor were replaced by a capacitor?

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medium

Explain why AC voltage is preferred over DC voltage for long-distance transmission of electrical energy.

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medium

Critique the statement: 'In a series LCR circuit at resonance, the individual voltages across the inductor and capacitor can be much larger than the source voltage, which violates the law of conservation of energy.'

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medium

A pure inductor with an inductance of

50

mH is connected to an AC source of

220

V,

50

Hz. Calculate the inductive reactance and the rms current in the circuit.

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hard

A series LCR circuit has

R = 10 \text{ } \Omega

,

L = 80

mH, and

C = 50 \text{ } \mu F

. It is connected to a variable frequency

200

V AC source. Calculate the impedance of the circuit and the amplitude of the current when the angular frequency of the source is

200 \text{ rad/s}

.

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hard

In a series LCR circuit,

R = 300 \text{ } \Omega

,

L = 0.9

H,

C = 2.0 \text{ } \mu F

, and the source is

V = 150

V with angular frequency

\omega = 1000

rad/s. Calculate the power factor and the average power dissipated in the circuit.

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hard

Summarize the phase relationship between the applied AC voltage and the resulting current in a purely resistive, a purely inductive, and a purely capacitive circuit.

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hard

Formulate a mathematical expression for the quality factor (Q-factor) of a series LCR circuit and justify its significance. Design a scenario where a high Q-factor is desirable and another where a low Q-factor is preferred.

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hard

Create a hypothetical scenario for an engineer designing a power supply for a sensitive electronic device that requires a low DC voltage from a standard high-voltage AC main. Propose a block diagram of the system they would need to build, justifying the function of each component, especially the transformer and a capacitor.

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hard

Explain the phenomenon of resonance in a series LCR circuit. State the condition for resonance and recall the formula for the resonant frequency.

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hard

Design a simple series LCR circuit that would resonate at a frequency of

1000

Hz. Propose specific values for L and C, and justify why your chosen values are practical for a laboratory setup. Also, evaluate the effect of adding a resistor with a high resistance value on the sharpness of resonance.

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hard

Design an experiment to verify the phase relationship between voltage and current in a purely capacitive AC circuit. Your design should include a circuit diagram, the equipment needed, the procedure, and a description of the expected output on a Cathode Ray Oscilloscope (CRO).

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hard

Evaluate the role of the power factor in industrial electricity billing. Why do power companies penalize industrial consumers with low power factors, and how can these consumers improve their power factor? Justify your answer.

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hard

Formulate a problem involving a series LCR circuit where the power factor is

0.5

(lagging). The circuit is connected to a

240 \text{ V}

,

50 \text{ Hz}

source, and has a resistance of

R = 30 \Omega

. Propose values for L and C that satisfy these conditions and then calculate the total impedance and the average power dissipated.

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hard

Analyze how connecting a capacitor of an appropriate value in parallel can improve the power factor of an inductive circuit where the current lags the voltage.

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hard

A

10 \text{ } \mu F

capacitor and a

50 \text{ } \Omega

resistor are connected in series to a

110

V,

50

Hz AC source. Calculate the rms current in the circuit. Also, calculate the rms voltage across the resistor and the capacitor. Demonstrate why the algebraic sum of these voltages is not equal to the source voltage.

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hard

Explain the function of a phasor in the analysis of AC circuits. Describe how phasors are used to represent AC voltage and current.

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hard

Propose a modification to a series LCR circuit, initially operating at a frequency below its resonance, to bring it into resonance without changing the source frequency. Justify two distinct methods to achieve this.

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Alternating CurrentClass 12 Physics Practice Questions