Magnetism Magnets l magnetism repulsion l not all

Magnetism

Magnets l magnetism repulsion l not all objects are affected by the force of magnetism l l – force of attraction or ex. wood, glass, paper, plastic common metals affected by magnetism are iron, nickel, and cobalt

Magnets ¶Atoms themselves have magnetic properties due to the spin of the atom’s electrons. ¶Groups of atoms join so that their magnetic fields are all going in the same direction ¶These areas of atoms are called “domains”

Magnets When an unmagnetized substance is placed in a magnetic field, the substance can become magnetized. This happens when the spinning electrons line up in the same direction.

Magnets l poles l – two ends of a magnet every magnet has two poles north (N) pole l south (S) pole l l even if you break a magnet in half, each half will have a north pole and a south pole

Properties of Magnets l like magnetic poles repel each other l unlike magnetic poles attract each other

Magnetic Fields l magnetic field – area around a magnet where magnetic forces can act l a magnetic field is made up of magnetic lines of force

Magnetic Fields l magnetic lines of force – lines that show the shape of a magnetic field l the magnetic lines of force are closest together at the poles of the magnet l this is where the magnet is strongest

Field Lines Around a Bar Magnet

Field Lines of Repelling Bars

Field Lines of Attracting Bars

If you cut a magnet in half, S N you get 2 magnets! S N

The Earth as a Magnet l the Earth has a North Magnetic Pole and a South Magnetic Pole l the North Magnetic Pole is located near the geographic North Pole l the South Magnetic Pole is located near the geographic South Pole

The Earth as a Magnet l the North Magnetic Pole is like the south pole of a bar magnet l the South Magnetic Pole is like the north pole of a bar magnet

The Earth as a Magnet l the Earth is surrounded by a magnetic field which extends far into space l magnetosphere magnetic field – region of the Earth’s

The Earth as a Magnet l the magnetosphere traps charged particles from the sun l when these particles enter the atmosphere, an aurora is formed l auroras are also called the northern and southern lights

Electricity and Magnetism l an electric current passing through a wire causes a magnetic field

Electricity and Magnetism l electromagnetism – relationship between electricity and magnetism

Electricity and Magnetism l electromagnetic induction – process by which an electric current is produced by moving a wire in a magnetic field

Electricity and Magnetism la wire carrying an electric current always has a magnetic field around it the magnetic field in a straight wire is not very strong l if the wire is wound into a coil, the magnetic field becomes much stronger as the individual magnetic fields overlap l l the greater the number of coils, the stronger the magnetic field

Electromagnets l electromagnet – temporary magnet made by wrapping a current-carrying wire around an iron core l the center of an electromagnet is called the core l it is often made of iron

Electromagnets l as long as current is flowing, an electromagnet has a magnetic field l when current is turned off, there is no longer a magnetic field

Electromagnets l there are two ways to make an electromagnet stronger l increasing the number of coils l increasing the amount of current

A Simple Electromagnet:

Electromagnets l electromagnets are useful because they can be turned on and off l electromagnets have many important uses l ex. radios, telephones, computers

Electromagnets l changing the direction of an electric current causes the poles of an electromagnet to reverse l this feature is important in the production of electric motors

Transformers l transformer – device in which alternating current in one coil of wire induces a current in a second coil

Transformers la transformer consists of two coils of wire around a magnet l the first coil, called the primary coil, is connected to the power source l the second coil, called the secondary coil, is connected to the load l a load is something that uses electricity, such as a light bulb or a motor

Transformers la transformer only works with alternating current

Transformers la l step-up transformer increases voltage it consists of more coils of wire in the secondary coil than the primary coil

Transformers la step-down transformer decreases voltage l it consists of more coils of wire in the primary coil than the secondary coil

Electric Motors l electric motor – device that changes electrical energy into mechanical energy

Electric Motors l an electric motor is made up of an electromagnet and a permanent magnet

Electric Motors l the electromagnet is free to turn and is hooked up to a source of alternating current l changing the direction of an electric current causes the poles of an electromagnet to reverse

Electric Motors l attraction and repulsion between the electromagnet and the permanent magnet cause the electromagnet to spin

Generators l generator – device that changes mechanical energy into electrical energy l a current can be induced in a loop of wire by spinning the loop inside a magnetic field l due to the changing direction of the wire, an alternating current is produced

Generators l an electric generator is made up of an insulated loop of wire and a U-shaped magnet l spinning the loop of wire in the magnetic field of the magnet produces an electric current

Generators l most of the energy we use every day comes from generators

Generators l mechanical energy for many generators is supplied by turbines l a turbine is a large wheel that is turned by moving steam or water