Q. A magnetic needle is placed on a cork floating in a still lake in the northern hemisphere. Does the needle together with the cork move towards the north of the lake
A) Yes
B) No
C) May be or may not be move
D) Nothing can be said
Explanation
(b) Magnetic needle is a dipole which is in earth’ uniform magnetic field and as a dipole in a uniform field does not experience any net force but may experience a couple as shown in figure, so the needle together with the cork will not translate $i.e.$ move towards the north of the lake, but rotate and set itself parallel to the field with it’s north pole pointing north
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.