How is torque produced in a current-carrying loop in a magnetic field?

Torque is produced in a current-carrying loop in a magnetic field due to the interaction between the magnetic field and the current.

In more detail, when a current-carrying loop is placed in a magnetic field, the magnetic field exerts a force on the current. This force is perpendicular to both the direction of the current and the magnetic field. This is known as the Lorentz force. The Lorentz force acting on different sides of the loop can create a turning effect or torque, causing the loop to rotate.

The magnitude of the torque depends on several factors. Firstly, it is directly proportional to the current flowing through the loop. The greater the current, the greater the force exerted by the magnetic field, and hence the greater the torque. Secondly, it is also directly proportional to the area of the loop. A larger loop means a larger area for the magnetic field to act upon, resulting in a larger torque. Thirdly, it depends on the angle between the plane of the loop and the magnetic field. The torque is maximum when the plane of the loop is perpendicular to the magnetic field.

The direction of the torque can be determined using Fleming's left-hand rule. If you point your thumb in the direction of the current and your index finger in the direction of the magnetic field, your middle finger will point in the direction of the force. This force is exerted in a direction that tends to rotate the loop.

In summary, the torque experienced by a current-carrying loop in a magnetic field is a result of the Lorentz force acting on the current in the loop. This force, being perpendicular to both the current and the magnetic field, creates a turning effect that can cause the loop to rotate. The magnitude and direction of this torque depend on the current, the area of the loop, the strength and direction of the magnetic field, and the angle between the plane of the loop and the magnetic field.