Question: Assertion (A): The deflecting torque acting on a current-carrying loop is zero when its plane is perpendicular to the direction of the magnetic field.
Reason (R): The deflecting torque acting on a loop of the magnetic moment if in a magnetic field, B is given by the dot product of it and B.
The correct answer is –
Explanation:
The deflecting torque acting on a current-carrying loop placed in a magnetic field is given by the equation:
τ = m x B
where τ is the deflecting torque, m is the magnetic moment of the loop, and B is the magnetic field. The symbol “x” denotes the vector product.
When the plane of the loop is perpendicular to the direction of the magnetic field, the angle between the magnetic moment vector and the magnetic field vector is 90 degrees. In this case, the vector product of the two vectors becomes maximum in magnitude, and the deflecting torque becomes maximum. However, the dot product of the two vectors becomes zero.
Therefore, assertion (A) is true, and reason (R) is false.
