Torque, also called moment or moment of force (see the terminology below), is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist.In more basic terms, torque measures how hard something is rotated. For example, imagine a wrench or spanner trying to twist a nut or bolt. The amount of 'twist' (torque) depends on how long the wrench is, how hard you push on it, and how well you are pushing it in the correct direction.The terminology for this concept is not straightforward: In physics, it is usually called 'torque', and in mechanical engineering, it is called 'moment'.However, in mechanical engineering, the term 'torque' means something different.
If the magnetic field B is parallel to the plane of a loop carrying
a current I, the torque exerted by B on the loop is IAB, where A is the area of the loop.
In general, the torque is given by I A x B, where A is a vector
whose magnitude is the loop area and which is directed normal to the loop plane.
The magnetic moment of a loop of area A carrying a current I is the
product m = IA and is directed normal to the plane of the loop: if the four fingers of the right hand circle
around in the direction of the current, then the thumb points in the direction of m.
The torque exerted by a magnetic field B on a magnetic moment m is
given by the cross product m x B. The potential energy of a magnetic dipole m in a magnetic field B is the dot
Torque on a Current Carrying Loop
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