Magnetism SPI 0807.12.3

Bell Work (get textbook) Grab a sheet of construction paper. Copy down your homework assignment or take a picture with your phone. It will be up the whole class period. Answer the following question: Why would this light turn on during this time of year?

Then start a new section called “Magnetic Fields” PUT HW IN BASKET. (CH 16 SEC. 1) Recently, scientists discovered that rainbow trout have tiny amounts of magnetic material in cells in their noses. Scientists think it might help them navigate. Answer the following IF questions for bell work in back of composition book. Do you think the magnetic material in the trout’s nose makes a strong magnet? Why or why not? What kind of material does a magnet stick to? Where do you encounter magnets in your everyday life? Then start a new section called “Magnetic Fields”

Objective: Distinguish between the earth’s magnetic field, a magnet, and the fields that surround a magnet and an electromagnet.

History Magnets have been known for centuries. The Chinese and Greeks knew about the “magical” properties of magnets. The ancient Greeks used a stone substance called “magnetite.” They discovered that the stone always pointed in the same direction. Later, stones of magnetite called “lodestones” were used in navigation.

Magnets magnetism – force of attraction or repulsion common metals affected by magnetism are iron, nickel, and cobalt

Magnets All magnets have a north and a south pole. poles – two ends of a magnet - comes in pairs (north/south) Even if you break a magnet in half, each half will have a north pole and a south pole.

Properties of Magnets LIKE poles repel each other OPPOSITE poles attract each other

Properties of Magnets When an object becomes magnetized its magnetic domains (groups of atoms) all line up in the same direction. When an unmagnetized substance is placed in a magnetic field, the substance can become magnetized.

Unmagnetized vs. Magnetized An un-magnetized substance looks like this… While a magnetized substance looks like this…

Magnetic Fields The region where the magnetic forces act is called the “magnetic field”. The magnetic lines of force are strongest at the poles of the magnet.

Draw and Label Note how the magnetic fields differ with the shape of the magnet. Horseshoe Magnet Bar Magnet Circle Magnet

Earth’s Magnetic Field Which of the following magnet’s magnetic field is most similar to the magnetic field of Earth?

Earth is like a Bar Magnet Both have magnetic field lines that emerge from their north poles.

The Earth as a Magnet The North Magnetic Pole is like the south pole of a bar magnet. The South Magnetic Pole is like the north pole of a bar magnet. The nickel iron core of the earth gives the earth a magnetic field much like a bar magnet. It is strongest near the North and South magnetic poles.

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

The Earth as a Magnet When the magnetic particles from the sun, called “solar wind”, strike this magnetosphere, we see a phenomenon.

The Northern Lights The Aurora Borealis in the Northern Hemisphere. And the Aurora Australias in the Southern Hemisphere.

AURORA BOREALIS NORTHERN LIGHTS

Objective: Distinguish between the earth’s magnetic field, a magnet, and the fields that surround a magnet and an electromagnet.

ASSESSMENT Please close your science notebook, get out a sheet of paper, and number 1-10.

ASSESSMENT The Magnetosphere Completely surrounds the Earth Is found only near Earth’s poles Exists over a region larger than Earth Two of the above

ASSESSMENT Many migrating birds Navigate using Earth’s magnetic field May be able to see Earth’s magnetic field Have natural “compasses” that they use for navigation All of the above

ASSESSMENT True or False Earth’s magnetic field extends outward from the planet in all directions

ASSESSMENT True or False Harmful particles from the sun are repelled by Earth’s magnetic poles.

1 Which type of magnet produces a magnetic field most similar to Earth’s? A. bar magnet B. horseshoe magnet C. electromagnet D. temporary magnet

2 Which of the following is found in all magnets? A. an electrical field B. a transformer C. a north pole and a south pole D. a geographic pole

3 Charged particles react with Earth’s _______________________ to form the Northern Lights (Aurora Borealis).   A. magnetic field B. water vapor C. pollution D. clouds

4 Which statement best compares the magnetic field of Earth to the magnetic field of a bar magnet? A. Magnetic field lines around Earth are symmetrical but magnetic field lines around a bar magnet are not symmetrical. B. Magnetic field lines around Earth are in a circular pattern but magnetic field lines around a bar magnet extend away from the magnet. C. Magnetic field lines for both Earth and a bar magnet are generated from convection currents. D. Magnetic field lines for both Earth and a bar magnet emerge from their north poles.

5 Which diagram shows a magnetic field most similar to the magnetic field of Earth?

6 Which of the reasons below explains how magnets can attract or repel objects without touching them? A. The gravitational force surrounding each magnet acts at a distance. B. The magnets share electrons and act at a distance. C. The magnets generate static electricity. D. A magnetic field surrounds a magnet and exerts a magnetic force.

7 Which magnet below would provide the best example for the magnetic poles and magnetic fields of Earth?

8. When you break an iron magnet into two pieces, you get __________________. A. two south poles B. a piece of iron that is no longer a magnet C. two north poles D. two north poles and two south poles

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BONUS: Northern Lights NITROGEN (N2) (what color?) OXYGEN (O2)  (what 2 colors?)