1 MAGNETISM

2 Describe magnetism Investigate applications of magnetism and its relationship to the movement of electrical charge as it relates to • electromagnets • simple motors • permanent magnets electromagnetic induction

force of attraction or repulsion due to electron motion. 3 Magnetism is the force of attraction or repulsion due to electron motion.

4 Magnets have two poles, a north pole and a south pole. Unlike magnetic poles attract each other, while like magnetic poles repel each other. 4

Materials with most of the domains lined up are considered magnetized. 5 Groups of atoms with magnetic poles aligned are called magnetic domains. Materials with most of the domains lined up are considered magnetized.

The more domains that are aligned, the stronger the magnetic field in the material. 6

7 Field lines were introduced by michael faraday , who named them ‘’lines of force.’’ Sketch this one

8

Magnetism From Electricity A connection between electricity and magnetism was discovered (accidentally) over 100 years ago, it was noticed that a compass needle is deflected when brought into the vicinity of a current carrying wire. Thus, currents can induce a magnetic field. An electromagnet is simply a coil of wires which, when a current is passed through, generate a magnetic field, as below. 9 Current gives rise to magnetic fields, just as electric charge gave rise to electric fields Electromagnet

10 The basic idea behind an electromagnet is extremely simple: By running electric current through a wire, you can create a magnetic field.

11 Electromagnets Electricity through the coiled wire creates a magnetic field which induces magnetism in the iron core. The domains in the core become aligned with the magnetic field of the coil.

A rotating electromagnet is used in an electric motor to convert electrical energy to mechanical energy. 12

When a magnet is moved near a wire, an electric current can be created When a magnet is moved near a wire, an electric current can be created. This process is called electromagnetic induction. Electromagnetic induction is used in the operation of a generator, a device that converts mechanical energy to electrical energy. In a generator, an electric current is produced when a coil of wire is rotated in a magnetic field. 13

14 Generating electricity: coil of wire rotated in a magnetic field magnet is moved near a wire

15 The use of magnetic waves to make pictures of the inside of the body. Using a large magnet, radio waves, and a computer, an MRI produces two-dimensional and three-dimensional pictures. July 3, 1977

Which of these correctly identifies both devices illustrated? 16 Which of these correctly identifies both devices illustrated? A Picture A: electric generator; Picture B:electromagnet B Picture A: electromagnet; Picture B: electric generator C Picture A: electric motor; Picture B: electromagnet D Picture A: electric generator; Picture B: electric motor

A magnetic field can be found in which 17 A magnetic field can be found in which of the following? A electric motor B sound wave C plastic cord D glass rod