How does Fleming's left-hand rule relate to motors?

Fleming's left-hand rule is used to predict the direction of motion in electric motors.

Fleming's left-hand rule, also known as the motor rule, is a simple way to remember the relationship between the direction of the magnetic field, the direction of the current, and the direction of the force in an electric motor. This rule is named after the British scientist John Ambrose Fleming, who introduced it in the late 19th century.

To apply the rule, you extend your left hand with the thumb, first finger and second finger all at right angles to each other. The First finger represents the direction of the Field (magnetic field), the seCond finger represents the direction of the Current, and the thuMb represents the direction of the Motion (force). This is often remembered using the acronym 'FCM'.

In the context of an electric motor, the current and magnetic field are inputs, and the motion is the output. When a current-carrying wire is placed in a magnetic field, it experiences a force. This force is what causes the wire (and therefore the motor) to move. By using Fleming's left-hand rule, you can predict the direction of this motion.

For example, if the magnetic field is directed north-to-south and the current is flowing east-to-west, then, according to Fleming's left-hand rule, the force (and therefore the motion of the motor) will be directed upwards. Conversely, if the current were flowing west-to-east, the motor would move downwards.

Understanding and applying Fleming's left-hand rule is crucial for anyone studying the operation of electric motors, as it allows you to predict the behaviour of the motor based on the direction of the current and the magnetic field. It's a fundamental principle that underpins the operation of all electric motors, from tiny ones in electric watches to huge ones in industrial machinery.