Class 10 Science Chapter 12: Magnetic Effects of Electric Current case study question with answers
One case-based question of the kind the board asks in Section E: a passage and a figure, then 3 parts worth 4 marks in all, with the answer and the marking scheme for each. Written from the NCERT chapter.
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Answer: (a) north
Right-hand thumb rule, thumb up along the current: seen from above the field lines go anticlockwise, so at P, which is east of the cable, the field points north.
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Answer: (a) smaller
The field decreases as the distance from the conductor increases; Q is farther from the cable than P.
Answer and marking scheme
Reversing the current reverses the field, so the north pole at P now points south. Doubling the current makes the field at P larger, so the cable's effect on the needle is stronger.
- needle at P turns to point south, as the field reverses (1)
- larger current gives a stronger field at P (1)
Answer and marking scheme
Right-hand thumb rule: hold the cable in the right hand with the thumb along the current; the fingers wrap round in the direction of the field lines. With the thumb pointing up, out of the shelf, the fingers curl anticlockwise as seen from above.
- right-hand thumb rule stated (1)
- anticlockwise seen from above (1)