Magnetic Fields What is a cow magnet Magnetic

Magnetic Fields

What is a cow magnet?

Magnetic Field Lines • Defined as the direction N pole of a compass points in the field. • Drawn from N to S

Lab Magnetic Fields • Mapping magnetic fields using the compass method

Lab Magnetic Fields • Use iron fillings poured over a piece of paper to visualize magnetic field of each magnet

Magnetic Flux • Number of field lines in any region • Greatest around the poles of a magnet

Fact or Fiction? • If a very strong magnet is brought near the corner of a dollar bill, the bill will be attracted.

What is the advantage of using a horseshoe magnet? • Poles are close together.

Which material affects a magnetic field? • • • Index cards Razor blade Stream of water Straight pin Aluminum foil • Only ______ substances can distort a magnetic field.

Metal detectors • Smart phones now have a built in magnetometer to detect magnets in addition to the Earth’s Magnetic Field.

How does an automatic traffic signal know that your car is there? • The coil of wire is in the street and when your car passes over it, that tells the signal to turn green.

Earth’s Magnetic Field • Earth has a magnetic field shaped similar to a big bar magnet. • Center of Earth is much too hot for domains to stay aligned. • Earth’s polarity can switch as well, which it has done so more than 170 times. (Last reversal 700, 000 years ago)

Aurora Borealis • Northern Lights

Aurora Borealis • High temperatures on the sun’s surface plasma produce _______, the fourth phase of matter consisting of charged particles. These charged particles travel throughout solar the solar system as _____ wind _____. When charged particles reach the region of the earth’s outer atmosphere called the magnetosphere ________, their motion is controlled by the earth’s magnetic field.

Aurora Borealis • The charged particles are able to slip through the earth’s magnetic field at the poles ______ and enter the atmosphere. electrons They collide with _______ in atoms of gases like oxygen and nitrogen energy and transfer _____, making the electrons jump to higher energy levels. When they fall, they give off visible light _____ of different colors.

Southern Lights • Aurora austrailis

Show what you know 1) Magnetic field lines are drawn a) from north to south c) from positive to negative b) from south to north d) from negative to positive 2) This diagram represents the magnetic field between a) two N poles b) two S poles c) N pole (left) and S pole (rt) d) S pole (left) and N pole (rt)

3) Magnetic flux is a) the number of magnetic field lines in an area b) an indication of the strength of a magnetic field c) greatest at the poles of a magnet d) all of these 4) The cause of the earth’s magnetic field is a) a giant bar magnet imbedded in the center of the earth b) the aligned domains in the iron rich solid core c) still unknown d) all of these 5) The Aurora Borealis a) originates on the sun as solar wind b) is caused by charged particles transferring energy to the atoms of gases in the atmosphere c) can only be seen at northern latitudes