First Five Silently enter the room and sit down in your assigned seat. Begin working on your Activator. When you’ve completed your Activator, read your DEAR book.

Today’s Objectives IWBAT… Compare Earth’s magnetic field to a bar magnet’s magnetic field by describing Earth’s magnetic field and identifying geographic and magnetic poles. Analyze the force of Earth’s magnetic field in order to explain how a compass works.

The Earth is a magnet!! Earth behaves as if it has a giant bar magnet moving through its core The magnetic field that is created around Earth is very similar to the magnetic field of a bar magnet

Poles The poles of this imaginary magnet are located near the Earth’s geographic poles However, these poles are opposite: The magnetic south pole is closest the geographic north pole The magnetic north pole is closest to the geographical south pole

There is iron in the core of the Earth The earth acts as if a giant bar magnet has been stuck through the middle of it since the center is primarily composed of iron and nickel. When the Earth rotates, electric currents flow in the iron

Compass A compass needle is a small magnet and the tip points to the geographic north pole Therefore, the point of a compass needle is attracted to the south pole of a magnet Compass needles and north poles of magnets point to Earth’s magnetic south pole, which is near Earth’s geographic north pole

Compass A compass always points towards North because the needle is attracted by the Earth’s magnetic field

A Magnetic Light Show An aurora is a beautiful curtain of light. Earth’s magnetic field plays a part in making auroras. An aurora is formed when charged particles from the sun hit the oxygen and nitrogen atoms in the air. The atoms become excited and then give off lights of many colors.

Earth’s magnetic field blocks most of the charged particles from the sun. But the field bends inward at the magnetic poles. As a result, the charged particles can crash into the atmosphere at or near the poles.

How to Make Your Own Compass 1) Rub a needle with a magnet quickly, this will make a magnetic field 2) Place the needle on a piece of sponge or cork 3) Place it in the water to float freely Watch and see! It will turn and face north!

The magnetic poles of the Earth are not quite lined up with the geographic poles of the Earth. The Earth’s field is like that of a giant bar magnet with the south magnetic pole located about 1300 miles from the geographic north pole (north of Hudson Bay in Canada). The north magnetic pole is about 1200 miles form the south geographic pole of the Earth. There is considerable geologic evidence that the magnetic poles move around and have even reversed themselves 9 times in the last 4 million years (evidence in the iron-rich basaltic rock that volcanoes have spewed forth over the ages. As that lava freezes it provides a snapshot of the Earth’s magnetic field at that time.) Also, the strength of the Earth’s field has decreased about 5% in the last 100 years—in another 1500 years or so the field could be very weak or even non-existent. The source of the Earth’s magnetic field is thought to be the spinning (because of Earth’s rotation) electrically conducting molten metal outer core deep within the Earth.

Why does this make sense? A compass needle points _______ because the magnetic pole of the Earth that is closest to the geographical North Pole is a magnetic south pole. Why does this make sense? The north pole of a compass will actually point to the Earth’s south magnetic pole (which is about 1300 miles away from the geographic north pole—more on that on a later slide in this chapter’s slides.)

Exit Ticket In the space below, draw Earth and its magnetic field. Label the geographic poles and the magnetic poles.