Question

A student performs an experiment to study the magnetic effect of current around a current-carrying straight conductor. He reports that:
(i) the direction of deflection of the north pole of a compass needle kept at a given point near the conductor remains unaffected even when the terminals of the battery sending the current in the wire are interchanged.
(ii) For a given battery current, the degree of deflection of a N-pole decreases when the compass is kept at a point farther away from the conductor.
Which of the above observations is correct and why?

Answer 1

(i) This observation is incorrect because the direction of the magnetic field around a conductor changes with the change in direction of the current flowing through it. Due to this change in the direction of the magnetic field, the direction of force acting on the north pole of the compass also changes.
(ii) This observation of correct because the magnitude of the magnetic field decreases with an increase in the distance from the current carrying conductor.