In this lesson you focused on the following essential questions:

  • What is the nature of the magnetic force acting on a current-carrying conductor in an external magnetic field?

  • How are magnetic forces used in a direct current motor?

  • How is a current produced by an electric generator?

In a similar way to that of a charge moving perpendicularly to a magnetic field, a magnetic force acts on a current-carrying conductor located perpendicularly in a magnetic field.  Electric current is measured in amperes (the amount of charge, in coulombs, passing a fixed point in a conductor each second).  Mathematically, it is expressed as

 

 

The direction and magnitude of the magnetic force acting on a current-carrying conductor is determined, respectively, by hand rules and the product of the current, length of wire in the field, and strength of the magnetic field.  Mathematically, it is expressed as

 

 

This equation describes the magnitude of the motor effect because the force can be used to rotate a conducting loop in an external magnetic field.

 

The direct current electric motor is essentially an electric generator in reverse.  When a conductor is forced through a non-parallel magnetic field, a current is induced in the wire.  This is known as the generator effect.  Furthermore, the direction of the induced current is such that it produces a magnetic field opposing the motion causing it.  This is known as Lenz's law.  Taken together, the motor effect and the generator effect are linked by the interaction of electric and magnetic fields.

 

Assignment 8

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