Question

A conductor is carrying a current(shown in black), and a magnet is placed next to it as shown. Now it is known that the magnet moves away from you perpendicular to the plane. What should be the current in another wire (shown in green) in order to keep the magnet in place? (Consider the force only on the north pole)

• A. Vertically upwards
• B. Vertically downwards
• C. Same as direction of current in wire 1
• D. Opposite to the direction of current in wire 1

Answer 1

Answer: (A), (C)

The correct options are
A Vertically upwards
C Same as direction of current in wire 1

The direction of magnetic field due to the first conductor should be directed into the plane of paper, as shown


Here, represents the field being directed into the plane of the paper. In other words, away from you.
Hence, the current in the first wire should be vertically upwards, using the right-hand thumb rule.
Now to keep the magnet in place, the magnetic field due to the second conductor should be towards you.

Here, represents the field being directed out of the plane of the paper. In other words, towards you.