Q. A cable carrying a direct current is burried in a wall which stands in a north-south plane. A horizontal compass needle on the west side of the wall is found to point towards south instead of north. The coil is laid
A) Vertically upwards and the current is also flowing upwards
B) Vertically upwards and the current is flowing down downwards
C) Horizontal with current from south to north
D) Horizontal with current from north to south
Explanation
(a) The magnetic needle will be deflected towards south if initially the direction of force on the needle due to current carrying conductor is towards west. It will be so if the direction of the current is vertically upwards and the wire is held vertically upwards (according to Fleming’s left hand rule).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.