Assertion (A) : With the help of compass, magnetic field lines can be traced outside the bar magnet.
Reason (R) : The north pole of a compass needle always points towards the south pole of the magnet when brought close to it.
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Model Answer
(C) Assertion (A) is true, but Reason (R) is false.
The compass can trace field lines outside the bar magnet (A is true). However, the north pole of the compass needle points towards the south pole of the magnet — meaning it is directed away from the north pole of the magnet, not towards the south pole as stated in R, which makes R false as worded.
(From Activity 12.3: "The south pole of the needle points towards the north pole of the magnet. The north pole of the compass is directed away from the north pole of the magnet.")
Explanation
- A is true: Activity 12.3 clearly shows a compass is used to draw/trace magnetic field lines outside a bar magnet.
- R is false: The textbook states that the south pole of the compass needle points towards the north pole of the magnet. So the north pole of the needle points away from the north pole — i.e., it points toward the south pole of the magnet. The Reason as written says "north pole of a compass needle always points towards the south pole," which is misleading/incorrect in general: it is only true near the south pole of the magnet, not everywhere outside it. More importantly, CBSE expects you to catch that R misstates the textbook's exact description, making it false.
- Examiners award the mark for choosing (C) with a brief justification.