List of top Physics Questions on Torque on a Current Loop

A circular coil of 30 turns and radius 8·0 cm carrying a current of 6 A is suspended vertically in a uniform horizontal magnetic field of 1·0 T. The field lines make an angle of 30\(^{\circ}\) with the plane of the coil. Calculate the magnitude of the external torque that must be applied to prevent the coil from turning. What would happen if the circular coil is replaced by a planar coil of irregular shape that encloses the same area, keeping other parameters unchanged?
A wire of length \(L\) is bent round into (i) a square coil having \(N\) turns and (ii) a circular coil having \(N\) turns. The coil in both cases is free to turn about a vertical axis coinciding with the plane of the coil, in a uniform, horizontal magnetic field and carry the same currents. Find the ratio of the maximum value of the torque acting on the square coil to that on the circular coil.
A circular coil of \(100\) turns and radius \[ \left(\frac{10}{\pi}\right)\text{ cm} \] carrying current \(5.0\) A is suspended vertically in a uniform horizontal magnetic field of \(2.0\) T. The field makes an angle \(30^\circ\) with the normal to the coil. Calculate:
(I) the magnetic dipole moment of the coil, and
(II) the magnitude of the counter torque required to prevent the coil from turning.
A rectangular loop of sides \(a\) and \(b\) carrying current \(I\) is placed in a magnetic field \(\vec B\) such that its area vector \(\vec A\) makes an angle \(\theta\) with \(\vec B\). With the help of a suitable diagram, show that the torque \(\vec \tau\) acting on the loop is given by \[ \vec \tau=\vec m\times \vec B, \] where \[ \vec m=I\vec A \] is the magnetic dipole moment of the loop.
A wire of length \(L\) is bent round into (i) a square coil having \(N\) turns and (ii) a circular coil having \(N\) turns. The coil in both cases is free to turn about a vertical axis coinciding with the plane of the coil, in a uniform, horizontal magnetic field and carry the same currents. Find the ratio of the maximum value of the torque acting on the square coil to that on the circular coil.
A circular coil of \(100\) turns and radius \[ \left(\frac{10}{\pi}\right)\text{ cm} \] carrying current \(5.0\) A is suspended vertically in a uniform horizontal magnetic field of \(2.0\) T. The field makes an angle \(30^\circ\) with the normal to the coil. Calculate:
(I) the magnetic dipole moment of the coil, and
(II) the magnitude of the counter torque required to prevent the coil from turning.
A rectangular loop of sides \(a\) and \(b\) carrying current \(I\) is placed in a magnetic field \(\vec B\) such that its area vector \(\vec A\) makes an angle \(\theta\) with \(\vec B\). With the help of a suitable diagram, show that the torque \(\vec \tau\) acting on the loop is given by \[ \vec \tau=\vec m\times \vec B, \] where \[ \vec m=I\vec A \] is the magnetic dipole moment of the loop.
Assertion-Reason Type Question Assertion (A): Torque acting on a current loop in a magnetic field is maximum when the plane of the loop is parallel to the magnetic field.
Reason (R): Torque on a magnetic dipole is given by: \[ \tau = MB\sin\theta \] where \(\theta\) is the angle between magnetic moment and magnetic field. Choose the correct answer from the options given below:
A straight wire loop carrying a current \( I \) sits flat inside a uniform, external magnetic field \( \vec{B} \). Under what orientation angle \( \theta \) between the normal vector of the loop surface and the magnetic field lines will the loop experience maximum torque?