6.11 Vocabulary Electromagnet: type of magnet in which the magnetic

field is produced by a flow of electric current Core: metal (iron) center of an electromagnet Coil: a spiral wire Motor: devices that use magnets to push and pull other

magnets and create motion and do work. Armature: the electromagnet inside a DC motor or AC

generator. AC generator: AC voltage source, powered by

electromagnetic induction electromagnetic induction: process by which AC

current is produced because current changes direction in the presence of a magnetic field.

Magnetism

PS-6.11 Explain the relationship of magnetism to the movement of electric charges in electromagnets, simple motors, and generators.

Electromagnets

Electric currents produce magnetic fields.

Electromagnets The fields can be concentrated

and thus strengthened by wrapping the wire in a coil.

More turns in the coil will strengthen the magnet.

Adding a core (like iron) will concentrate the magnetic field and strengthen the magnet.

The electromagnet can also be strengthened by increasing the current in the coil.

Motors Electric motors change

electric energy to mechanical energy by running an electric current through coils to make an electromagnetic. Motors use magnets to

push and pull other magnets and create motion.

Motors use the magnetic force from magnets to spin an armature (usually an

electromagnet).

DC Motor

                  

A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.

                  

The armature still rotates.

                  

When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats.

AC Generators

When a wire or a coil of wire moves through a magnetic field an electric current can be produced. This is called electromagnetic induction.

Generators Generators use

electromagnetic induction to produce and electric current.

A generator is similar to an DC electric motor.

A generator changes mechanical energy into electric energy by moving a coil past a magnetic field.

Generators produce AC current.

Review!! What is an electromagnet? What metals make a good core for an

electromagnet? How can we increases the strength of an

electromagnet? What is a motor? When the electric current stops running

through an electromagnet, what happens to the magnetism?

Review!! Why are electromagnets useful when

compared to permanent magnets? What is electromagnetic induction? What type of energy transformation takes

place in a motor? What type of energy transformation takes

place in a generator? What type of current do most generators

produce? Give an example of a practical use of

electromagnets.