Answer to Question #113783 in Electricity and Magnetism for Erica

Question

Briefly explain the motor effect, including the direction of deflection (motion). Your response should include five main points about the motor effect.

Answer 1

The motor effect is the phenomenon when a wire with current experiences forces when it is subjected to magnetic field. The magnitude of the force that the wire will experience is

$$F=IBL\text{ sin}\theta,$$

where theta - angle between the wire (or direction of the current) and the magnetic field lines.

1. As we see, if we put the wire parallel with the axis that connects south and north pole of magnet, the force will be zero.
2. If the magnetic field is zero, the wire with current won't experience any force.
3. If the field is infinitesimally small of if the wire is too short, the force will be zero
4. If the current is zero, strong field will not cause any force.

Left-hand rule: if you put your left hand so that the middle finger is oriented in the direction of current (yellow arrow), if the field (green) is directed into your opened palm, the thumb will show the direction of the force (blue arrow) like this: