NCERT Solutions Curiosity Chapter 4 –51Section 4.1.1 Electromagnets — Activity 4.4: Let us investigate

Book page 50 Updated on2026-09-05

Q1.
Connect the coil to the cell and observe the compass. Note down which pole of the magnetic compass is attracted to end A.
Answer

In the set-up shown in Fig. 4.4a it is the north pole of the compass needle (the red tip) that swings towards end A.

North pole of compass is attracted to end A
Unlike poles attract
Therefore end A is the South pole of the electromagnet
Why this is a valid test: you already know from Grade 6 that unlike poles (North–South) attract and like poles repel. The compass needle is a magnet whose poles you know. So whichever pole of the needle is pulled towards end A must be the opposite of end A — the needle is being used as a ready-made pole detector.
Check it yourself: your own coil may give the opposite answer, and that is not a mistake. Which end is North depends on the direction in which you wound the wire and on which way round you joined the cell. Record what your compass shows.
Q2.
Repeat this procedure to find the polarity of end B as well (Fig. 4.4b). Did you find that the polarity of end B is opposite to the polarity of end A?
Answer

Yes. At end B the other pole of the compass needle is attracted, so end B is the North pole while end A is the South pole.

End of the coilPole of the compass needle attracted to itPolarity of that end
ANorthSouth
BSouthNorth
Why they must be opposite: the same current goes round every turn of the coil in the same sense, so the coil's magnetic field runs along the axis in one direction only — out at one end and in at the other. A magnet cannot have two North ends. That is why an electromagnet, just like a bar magnet, always has one North and one South pole.
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