Class 12 Physics Assertion Reason Questions Chapter 7 Alternating Current

Download the chapter on Alternating Current from the CBSE Class 12 Physics Assertion Reason Questions. Class 12 Physics Assertion Reason Questions with Answers were created using the most recent exam format. To gauge their degree of preparedness, students can complete the NCERT Class 12 Physics Chapter 7 Alternating Current.

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Alternating Current Class 12 Assertion Reason Questions

The following questions consist of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.

Assertion (A): Alternating current (AC) changes direction periodically.
Reason (R): In an AC circuit, the direction of the current changes periodically with time, creating a sinusoidal waveform.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): In an AC circuit, the instantaneous value of voltage and current can be represented by sine functions.
Reason (R): The voltage and current in an AC circuit vary sinusoidally with time and can be expressed as V(t) = Vm sin(ωt) and I(t) = Im sin(ωt + φ), respectively.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): The root mean square (rms) value of an AC voltage is equal to its peak value multiplied by 0.707.
Reason (R): The rms value of an AC voltage is given by Vrms = Vm/√2, where Vm is the peak voltage value.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): The instantaneous power in an AC circuit oscillates at twice the frequency of the AC supply.
Reason (R): The instantaneous power in an AC circuit is given by P(t) = V(t) × I(t), and since both voltage and current vary sinusoidally, the power oscillates at twice the frequency.

Answer: (c) A is true but R is false.


Assertion (A): Transformers work on the principle of electromagnetic induction.
Reason (R): Transformers use two coils wound on a soft iron core, and the varying magnetic field in one coil induces an EMF in the other coil.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): The power consumed in a purely resistive AC circuit is constant with time.
Reason (R): In a purely resistive AC circuit, the voltage and current are in phase, resulting in a constant power consumption throughout the AC cycle.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): The power factor in an AC circuit is the cosine of the phase difference between voltage and current.
Reason (R): The power factor is defined as the ratio of the true power (P) to the apparent power (S) and is equal to cos(φ), where φ is the phase difference between voltage and current.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): A capacitor in an AC circuit allows the flow of alternating current.
Reason (R): In an AC circuit, a capacitor alternately charges and discharges, allowing the flow of alternating current through it.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): The impedance of an inductor in an AC circuit depends on the frequency of the AC supply.
Reason (R): The impedance of an inductor is given by XL = 2Ï€fL, where f is the frequency of the AC supply and L is the inductance.

Answer: (a) Both A and R are true and R is the correct explanation of A.


Assertion (A): An ideal inductor has zero resistance.
Reason (R): An ideal inductor is a purely inductive element with no resistance, which means it does not dissipate power in the form of heat.

Answer: (b) Both A and R are true but R is not the correct explanation of A.


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