Three plotting compasses are placed close to a current carrying wire wrapped around an insulator as shown in fig.How many compass needles will change direction if the current through the wire is increased?

Asked by m.nilu | 18th Nov, 2018, 10:27: AM

Expert Answer:

At the locations, where compass A and compass C are placed as shown in figure, magnetic field lines are parallel to axis of coil. 
Note that axis of coil is marked in figure. Field lines are marked in blue colour. compass deflection is shown in red color.
At the location, where compass B is placed, field lines are making some angle with the direction of axis of the coil.
This angle depends on the current passing through the coil.
Hence only deflection of compass-B will change according to the current passing through the coil.

Answered by Thiyagarajan K | 18th Nov, 2018, 10:50: PM

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