Explain how an electric motor works, including a discussion of the right-hand rule.

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enotechris's profile pic

enotechris | College Teacher | (Level 2) Senior Educator

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The Right Hand Rule is a useful mnemonic to spatially relate the force and velocity of a positively charged particle in a magnetic field.  Holding your hand as if you were going to shake someone else's, your thumb pointing up is the direction of velocity (conductor), your fingers pointing out is the direction of the magnetic field (flux), and your palm pointing to the left is the direction of the force (current). Force is thus perpendicular to velocity and magnetic field, or, if considering a motor, current is perpendicular to conductor and flux.

A motor works because 2 magnetic fields are interacting with each other, one from a fixed magnet and the other from an electromagnet.  The armature of a motor is an electromagnet with North and South polarities, and these interact with the North and South polarities on the magnet that encases the armature.  The North and South poles of the magnet repulse the North and South poles of the armature, causing the armature to spin. See graphic at the links:

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

An electric motor is used to convert electrical energy into mechanical one. Electric motors run by electromagnetism.

There are 3 basic elements which are interacting to produce motion:

  1. Magnetic flux (the motor housing generates magnetic field, due to the permanent magnets content)
  2. Current (when electricity is applied across the motor terminals, current flows through from one end of the terminal to the brush, commutator then to the windings, back to the commutator and brush and out through the other terminal.)
  3. Force (electromagnetic force which causes rotation of the shaft is produced by the current which flows through magnetic field. Switching of  current producing the rotating force which is called torque)

Magnitude of the force felt by a charge q moving with velocity v through a magnetic field B is:

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