Compass

Exit ticket: “A compass works by _______________ force Exit ticket: “A compass works by _______________ force. This force comes from Earth and acts ____ ______ ____________________ (without touching.)”

Review yesterday… Static electricity Remember that electrons can move around inside an object to create a more positive side or a more negative side. We have explored a force for the past few days that acts at a distance. What was that force? Static electricity Notice that the spheres are not touching – this is an “at-a-distance” force.

Other At-A-Distance Forces? Turn and talk for 15 seconds Are there any other forces you can think of that act without touching? Today’s Topic… MAGNETISM

Refresh your memory from Elementary…. What materials will be attracted by a magnet?

Watch as your teacher performs some magic Or click on this video to see the magic (watch only 2 minutes)

Can you explain this diabolical motion? Very strong magnets, like this one made from a rare Earth element called Neodymium, are attracted to the slight difference in charge of a water molecule, with hydrogens on one end and oxygen atoms on the other end. When a magnet is brought close to a grape, it makes those little water molecules spin, and this spinning makes the whole grape move! Turn and talk – 30 seconds It’s all about the water in the grape

Now check out a compass… Ask yourself questions then answer them with mini-experiments to figure out how it works. (If you already know how it works, guide your group to some good questions.) Complete the worksheet as you ask and answer at least 3 questions.

For example… CAUSE You might do a little mini- experiment holding the compass in three different positions to see where the needle can move freely. EFFECT Then write down your observations of how the compass reacts. Finally, write an inference which answers your original question, based on your observations. You might notice that the needle thingy in the middle is sitting in some liquid. You might ask the question, “Does the compass have to be held level to work?”

GO ! Conduct 3 mini-experiments observing cause and effect. Write them down!

Explain (give your inferences)

The compass works using magnetism, right? What would happen if a magnet was brought close to the compass? Go check it out! Write down your inferences.

Why? MAGNETIC FORCE Remember Newton’s 1st Law? The needle will stay at rest unless an unbalanced force comes along, so the magnet must be using some invisible, at-a-distance force. MAGNETIC FORCE Why do you think magnets make the compass go all wonkey, and not point to north anymore? Turn and talk – 15 seconds That’s right – the force of attraction of the magnet is stronger than the force of attraction of Earth.

Why? Did you notice that now the NORTH end of the compass needle is now attracted to the NORTH end of the magnet? What the heck? Don’t like poles repel each other?

Expand your knowledge of magnets… Click on the picture to launch the video

Now discuss.. Lodestone is made of a mineral now called magnetite. Original compasses were made from a material called lodestone. The Greeks discovered that if the loadstone was suspended, the pointy pieces would all point the same way. They called this way “north.” Lode anciently meant “to lead,” so a lodestone led the course for ships. You may have seen polished pieces of magnetite for sale.

In reality, the “north” end of the lodestone was attracted to a magnetic south pole. (Remember that opposites attract?) So what we call the geographic North Pole is actually the magnetic South Pole. (write this down and draw a model) That’s why what we call the “north” end of the compass is attracted to the north end of a magnet.

Comprehension Check: If you were in an airplane, and you flew north from here, up through Canada, over the Arctic Circle, and then down through Russian Siberia, what would happen to the needle on your compass? Turn and talk for 30 seconds…

Tasks: Tape your worksheet into your note book Complete your exit ticket: “A compass works by _______________ force. This force comes from Earth and acts ____ ______ ____________________ (without touching.)”