Question

(A) A vertical wire is carrying a current in the upward direction. It is placed in a magnetic field, pointing towards the East direction. Find out the direction of force on the wire.

(B) Out of two current carrying circular coils, coil 'A' has 10 turns while coil 'B' has 15 turns. Which of the two coils will produce a stronger magnetic field at its centre if same current is flowing through both the coils? Explain with reason.

(C) In the given figure, AB and CD are two magnetic field lines intersecting each other at point O. If a compass needle is placed at point O, what will happen? State your conclusions.

Accepted Answer

(A) Towards West. (B) Coil B produces stronger magnetic field because B is proportional to turns N. (C) Needle cannot point in two directions, proving magnetic field lines never intersect.. (A) Using **Fleming's Left-Hand Rule**: - Forefinger = Magnetic field (East) - Middle finger = Current (Upward) - Thumb = Force direction $\implies$ **West**. (B) **Coil B** produces a stronger magnetic field. *Reason:* The magnetic field produced at the center of a circular coil is directly proportional to the number of turns ($B \propto N$). Since coil B has 15 turns compared to 10 turns in coil A, $B_B > B_A$. (C) If a compass needle is placed at point O, it would try to align along two tangents simultaneously, which is impossible. Hence, **two magnetic field lines can never intersect each other**.

Magnetic Effects of Electric Current

Explanation

Practise this under board exam conditions