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Vinita and Ahmed… (Class 10 Science SQP 2023-24, Q39)

questionbuddy.in/q/cbse-10-science-2023-24-sqp-q39-vinita-ahmed-demonstrated-circuit-operates

ScienceCBSE Class 10 · Sample paper, session 2023-24 · 4 marks · Case-based

CBSE Class 10 Science sample paper 2023-24: question 39

From the official CBSE sample question paper for 2023-24, section E, question 39, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q39 · 4 marks · Case-basedCompetency-basedElectricity

Vinita and Ahmed demonstrated a circuit that operates the two headlights and the two sidelights of a car, in their school exhibition. Based on their demonstrated circuit, answer the following questions.

  1. (i)(a)

    State what happens when switch A is connected to Position 2.

    1 mark
  2. (i)(b)

    State what happens when switch A is connected to Position 3.

    1 mark
  3. (ii)

    Find the potential difference across each lamp when lit.

    1 mark
  4. (iii)(a)

    Calculate the current in each 12 Ω lamp when lit.

    1 mark

  5. OR

    (iii)(b)

    Calculate the current in each 4 Ω lamp when lit.

    1 mark

  6. OR

    (iv)

    Show, with calculations, which type of lamp, 4.0 Ω or 12 Ω, has the higher power.

    2 marks

Figure in the paper: Circuit diagram: a 12 V battery connected to a switch A with three positions (1, 2, 3). Position 1 connects directly to the main line feeding the lamps. Position 2 connects to the right-hand branch carrying two lamps of 12 Ω each; Position 3 connects to the middle branch carrying two lamps of 4.0 Ω each. The four lamps (two 4.0 Ω and two 12 Ω) are arranged in parallel between the top and bottom rails, with the two 4.0 Ω lamps on the left and the two 12 Ω lamps on the right. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.

Hints

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

Hint 1

Trace which branch of lamps the switch connects to the battery in each position.

Hint 2

In a parallel circuit, what is the voltage across each branch compared with the battery?

Hint 3

Use for current. For power with the same voltage, is the easiest form.

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)(a) With switch A at Position 2, only the branch with the two 12 Ω lamps is connected to the battery. Only the two 12 Ω lamps light up; the 4 Ω lamps stay off.

    ½ mark

  2. (i)(b) With switch A at Position 3, only the branch with the two 4 Ω lamps is connected. Only the two 4 Ω lamps light up; the 12 Ω lamps stay off.

    ½ mark

  3. (ii) All the lamps are connected in parallel directly across the 12 V battery. In a parallel connection, every branch gets the full supply voltage. So the potential difference across each lamp = 12 V when lit.

    1 mark

  4. (iii)(a) Each 12 Ω lamp has V across it. By Ohm's law, .

    1 mark

  5. (iii)(b) Each 4 Ω lamp has V across it. By Ohm's law, .

    1 mark

  6. (iv) (alternative to (iii)) Use . The voltage is the same (12 V) for every lamp because they are in parallel.

    • 4 Ω lamp:
    • 12 Ω lamp:
    1½ marks

  7. Since , the 4.0 Ω lamps have the higher power.

    ½ mark

Answer: (i)(a) Only the 12 Ω lamps light; (i)(b) only the 4 Ω lamps light. (ii) 12 V across each lamp. (iii)(a) 1 A; (iii)(b) 3 A. OR (iv) 4 Ω lamp: 36 W, 12 Ω lamp: 12 W, so the 4 Ω lamp has higher power.

Where the marks are

  • States only the 12 Ω lamps light at position 2 (0.5 mark)
  • States only the 4 Ω lamps light at position 3 (0.5 mark)
  • 12 V across each lamp, with reason that the lamps are in parallel (1 mark)
  • Current in each 12 Ω lamp = 1 A using (1 mark)
  • Current in each 4 Ω lamp = 3 A using (1 mark)
  • OR: uses with the same V for all lamps, gets 36 W and 12 W, and concludes the 4 Ω lamp has higher power (2 marks)

Revise the chapter

Practise this chapterBoard-style questions from Electricity, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2023-24: 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.