 Question For the primary school level, the student is expected to calculate how much electricity is flowing through the circuit and how much each bulb will receive in simple terms of electrical units. The brightness of the bulb will correspond to how much electrical units it receives (assuming the bulb doesn’t fuse).

Important:

• Circuits arranged in series have only one pathway in which electricity can flow through
• Circuits arranged in parallel have more than one pathway for electricity to flow through
• The units of electricity flows through each pathway and shares the units of electricity equally among the bulbs in the same pathway

For all four setups, there are 2 batteries so we can take it as 2 units of electricity.

• For circuit P, arranged in series, there is only one pathway for electricity to flow through. That pathway has 3 bulbs, so each bulb (including bulb A) will receive 2/3 units of electricity.
• For circuit Q, arranged in parallel, there are 3 pathways for electricity to pass through. Each pathway only has 1 bulb, so each bulb (including bulb B) will receive the full 2 units of electricity.
• For circuit R, arranged in parallel, there are 2 pathways for electricity to pass through. Each pathway has 2 bulbs, so the electrical units will be divided equally among them, with each bulb (including bulb C) receiving 1 unit of electricity each.
• For circuit S, arranged in parallel, there are 2 pathways for electricity to pass through. Each pathway also has 2 bulbs similar to circuit R. Therefore, each bulb (including bulb D) will receive 1 unit of electricity each.

Therefore, the amount of units of electricity for each bulb becomes:

 Bulb Units of electricity A 2 / 3 B 2 C 1 D 1

This is why the answer is B.

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B is the correct answer

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As each bulb in circuit Q receives the full voltage across it, the current passing through the bulbs are the same and the greatest compared to other circuits. Brightness of the bulb depends on the current thro it and the voltage across it.

Mrs Setho here. Email : sethophysicstuition@gmail.com

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(2) B

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Thank you!

🙂

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