Question

A current carrying coil ABCD is kept in uniform magnetic field as shown in the figure. Which of the following statements are correct?

• A. AB and CD are always at right angles to the field.
• B. At AB, the magnetic force acts into the plane perpendicular to the field.
• C. At CD, the magnetic force acts out of the plane perpendicular to the field.
• D. The net force acting on the coil is not always zero.

Answer 1

Answer: (A), (B), (C)

The correct options are
A AB and CD are always at right angles to the field.
B At AB, the magnetic force acts into the plane perpendicular to the field.
C At CD, the magnetic force acts out of the plane perpendicular to the field.

In the given case where a current carrying coil ABCD placed in uniform magnetic field, the sides AB and CD will always be at right angles. i.e. perpendicular to the magnetic field. Applying Fleming's right hand rule, the direction of magnetic force acting on the side AB will be into the plane perpendicular to the field and at CD, it will be out of the plane. So, the net force will be zero as the same amount of force acts on the opposite sides of the coil but in opposite directions.