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Alternating Current - ISC Class 12 Physics Questions with Answers, Page 2

56 past-paper questions on Alternating Current from ISC Class 12 Physics papers (2027-2018), newest first, in full. Questions 21-40 are on this page, 20 to a page. Tap "Show answer" under a question to see its answer.

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2025 · 5 marks · NumericalOpen: An alternating emf is applied to a circuit containing a resistor connected in…

Solve the following.

An alternating emf $E = 5.0 \sin(314t)\text{ V}$ is applied to a circuit containing a resistor connected in series with an unknown component X. The current in the circuit is found to be $I = 3.0 \sin\left(314t - \frac{\pi}{3}\right)\text{ A}$.
(a)[1.0]
Identify the component X.
(b)[1.0]
Calculate rms value ($I_{\text{rms}}$) of the current flowing through the circuit.
(c)[1.0]
Find the frequency of the source.
(d)[1.0]
Calculate power factor.
(e)[1.0]
Find the impedance ($Z$) of the circuit.

No answer yet.

2025 · 3 marks · NumericalOpen: An arc lamp takes 10 A at 50 V. Calculate the impedance of a choke of 1-ohm…

Solve the following.

An arc lamp takes 10 A at 50 V. Calculate the impedance of a choke of 1-ohm resistance to be connected in series with an arc lamp so that the lamp may be used on 200 V, 50 Hz supply. Use the data from the circuit diagram and the phasor voltage triangle and calculate the total active power and the power factor. AB – drop across arc lamp BC – drop across 1-ohm resistance of the choke CD – drop across the inductor BD – total drop across the choke

No answer yet.

2025 · 1 mark · MCQOpen: The graphs shown below are for three different Inductance, Capacitance, and…

Choose the correct option.

The graphs shown below are for three different Inductance, Capacitance, and Resistance (LCR) circuits (1), (2), and (3). Identify their nature based on the phase difference between $V_S$ and $I$.
  • (a)Inductive, Capacitive, and Resistive.
  • (b)Capacitive, Resistive, and Inductive.
  • (c)Resistive, Capacitive, and Inductive.
  • (d)Inductive, Resistive, and Capacitive.

No answer yet.

2025 · 3 marks · MatchOpen: Match the following conditions for an LCR series circuit with the corresponding…

Answer the following.

Match the following conditions for an LCR series circuit with the corresponding phase relation between current and voltage:
Column A
  • 1$\omega L > 1/\omega C$
  • 2$\omega L < 1/\omega C$
  • 3$\omega L = 1/\omega C$
Column B
  • (i)The current is in phase with voltage V.
  • (ii)The current lags in phase with voltage V.
  • (iii)The current leads in phase with voltage V.

No answer yet.

2025 · 5 marks · Short answerOpen: Three students, X, Y and Z performed an experiment for studying the variation…

Answer the following.

Three students, X, Y and Z performed an experiment for studying the variation of a.c. with frequency in a series LCR circuit and obtained the graphs as shown below. They all used an AC source of the same emf and inductance of the same value.
Figure for this question
(a)[1.25]
Who used minimum resistance?
(b)[1.25]
In which case will the quality Q factor be maximum?
(c)[1.25]
What did the students conclude about the nature of impedance at resonant frequency ($f_0$)?
(d)[1.25]
An ideal capacitor is connected across $220\text{ V}$, $50\text{ Hz}$, and $220\text{ V}$, $100\text{ Hz}$ supplies. Find the ratio of current flowing through it in the two cases.

No answer yet.

2024 · 5 marks · NumericalOpen: A , ac source is connected to a coil having coefficient of self-inductance of…

Answer the following.

(a)[2.5]
A $220\text{ V}$, $50\text{ Hz}$ ac source is connected to a coil having coefficient of self-inductance of $1\text{ H}$ and a resistance of $400\,\Omega$. Calculate: (1) the reactance of the coil. (2) the impedance of the coil. (3) the current flowing through the coil.
(b)[2.5]
Draw a labelled graph showing variation of impedance (Z) of a series LCR circuit vs frequency (f) of the ac supply. Mark the resonant frequency as $f_0$.

Draw: labelled graph showing variation of impedance (Z) of a series LCR circuit vs frequency (f) of the ac supply

Must show: impedance Z on y-axis, frequency f on x-axis, minimum impedance Z = R at resonant frequency f0

No answer yet.

2023 · 5 marks · NumericalOpen: A resistor, a inductor and a capacitor are connected in series to an ac supply…

Solve the following.

A $60\,\Omega$ resistor, a $1\cdot0\text{ H}$ inductor and a $4\mu\text{F}$ capacitor are connected in series to an ac supply generating an emf $e = 300\sin(500t)\text{ V}$. Calculate:
(a)[2.0]
impedance of the circuit.
(b)[1.5]
peak value of the current flowing through the circuit.
(c)[1.5]
phase difference between the current and the supply voltage.

No answer yet.

2023 · 5 marks · NumericalOpen: An ac generator generates an emf which is given by . Calculate: (1) frequency…

Solve the following.

(a)[2.0]
An ac generator generates an emf which is given by $e = 311\sin(240\pi t)\text{ V}$. Calculate: (1) frequency of the emf. (2) r.m.s. value of the emf.
(b)[3.0]
The primary coil of a transformer has $60$ turns whereas its secondary coil has $3000$ turns. (1) If a $220\text{ V}$ ac voltage is applied to the primary coil, how much emf is induced in the secondary coil? (2) If a current of $5\text{ A}$ flows in the primary coil, how much current will flow in a load in the secondary coil? State the assumption you have made regarding the transformer, in this calculation.

No answer yet.

2023 · 5 marks · NumericalOpen: An resistor, a inductor and a capacitor are connected in series to an a.c…

Solve the following.

An $80\,\Omega$ resistor, a $1\cdot0\text{ H}$ inductor and a $40\,\mu\text{F}$ capacitor are connected in series to an a.c. supply of $220\text{ V}$ such that the circuit draws the maximum current. At this stage, calculate:
(a)[1.0]
Resonant frequency of the circuit.
(b)[1.0]
Capacitive reactance of the circuit.
(c)[1.0]
Impedance of the circuit
(d)[1.0]
Current flowing through the circuit.
(e)[1.0]
Phase difference between capacitive and inductive voltages.

No answer yet.

2022 · 1 mark · MCQOpen: An A.C. generator generating an e.m.f of is connected to a series combination…

Choose the correct option.

An A.C. generator generating an e.m.f of $\varepsilon = 300 \sin (100\pi) t$ is connected to a series combination of $16\ \mu\text{F}$ capacitor, $1\text{ H}$ inductor and $100\ \Omega$ resistor. What is the frequency of A.C.?
  • (a)$100\text{ Hz}$
  • (b)$50\text{ Hz}$
  • (c)$300\text{ Hz}$
  • (d)$25\text{ Hz}$

No answer yet.

2022 · 3 marks · Case basedOpen: A capacitor, resistor and inductor are connected in series with an ac source…

Study the information given and answer the questions that follow.

A $2\ \mu\text{F}$ capacitor, $100\ \Omega$ resistor and $8\text{ H}$ inductor are connected in series with an ac source. At a certain frequency of about 40 Hz for this ac source, the current drawn in the circuit is maximum. If the peak value of e.m.f. of the source is 200V:
(i)[1.0]
What is the peak value of current in the circuit?
  • (a)$1.4\text{ A}$
  • (b)$2.2\text{ A}$
  • (c)$2.0\text{ A}$
  • (d)$1.8\text{ A}$
(ii)[1.0]
What is the phase relation between voltages across inductor and resistor?
  • (a)$\pi/2\text{ radian}$
  • (b)$\pi/3\text{ radian}$
  • (c)$\pi/4\text{ radian}$
  • (d)$\pi\text{ radian}$
(iii)[1.0]
What is the phase difference between voltages across inductor and capacitor?
  • (a)$\pi/2\text{ radian}$
  • (b)$\pi/3\text{ radian}$
  • (c)$\pi/4\text{ radian}$
  • (d)$\pi\text{ radian}$

No answer yet.

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