Skip to content

An alternating voltage of 220… (Class 12 Physics 2023, Q27)

questionbuddy.in/q/cbse-12-physics-2023-55-5-1-q27-alternating-voltage-applied-across-device

PhysicsCBSE Class 12 · Board exam 2023, set 55/5/1 · 3 marks · Short answer

CBSE Class 12 Physics 2023: question 27

Set in the CBSE Class 12 board exam of 2023, paper 55/5/1, section C, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerAlternating Current

An alternating voltage of 220 V is applied across a device X. A current of 0.22 A flows in the circuit and it lags behind the applied voltage in phase by radian. When the same voltage is applied across another device Y, the current in the circuit remains the same and it is in phase with the applied voltage.
(i) Name the devices X and Y and,
(ii) Calculate the current flowing in the circuit when the same voltage is applied across the series combination of X and Y.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 55/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Which circuit element makes the current lag by exactly 90°, and which keeps it in phase?

Hint 2

In series LR, Z = √(R² + X_L²).

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (i) In X the current lags the voltage by , so X is a pure inductor. In Y the current is in phase with the voltage, so Y is a pure resistor.

    1 mark

  2. (ii) Inductive reactance: .

    ½ mark

  3. Resistance: .

    ½ mark

  4. For the series combination: .

    ½ mark

  5. Current: A.

    ½ mark

Answer: (i) X: inductor, Y: resistor; (ii) I ≈ 0.16 A (0.11√2 A)

Where the marks are

  • X identified as inductor (½ mark)
  • Y identified as resistor (½ mark)
  • X_L = 1000 Ω (½ mark)
  • R = 1000 Ω (½ mark)
  • Z = 1000√2 Ω (½ mark)
  • I ≈ 0.16 A (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Alternating Current, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 55/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.