Module 4
1. Module 4
1.22. Page 7
Module 4—Magnetic and Electric Fields in Nature and Technology
Lesson Summary
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, since 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, which opposes 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.
Lesson Glossary
electric current: the amount of charge, in coulombs, that passes a fixed point in a conductor in a one-second interval
The unit of current is the ampere, equivalent to one coulomb of charge passing a fixed point in a conductor in a one-second interval.
generator effect or electromagnetic induction: the production of electrical current by the relative motion of a conductor in a magnetic field
Lenz’s law: the direction of a magnetically induced current is orientated such that it produces a magnetic field that opposes the motion causing it
motor effect: the magnetic force produced when a current-carrying conductor is located in a perpendicular magnetic field