Objective: SWBAT explain how magnetic forces on earth impact navigational compasses by engaging with a text on Earth’s magnetic field.
Do Now:
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Question 1
1.
In the center of a compass, there is a small magnet called a needle that points north. When a compass is turned, the needle will rotate until it points north again.
Why do you think a compass needle always points north? (Write your initial ideas. It is OK if you are unsure about them.)
"I think a compass needle always points north because ... "
Guided Notes:
Vocabulary:
Attract: to pull objects toward one another
Repel: to push objects away from each other
Isolate- to separate or set apart
Magnetic pole- one of the two opposite ends of a magnet
Model- an object, diagram, or computer program that helps us understand something by making it simpler or easier to see
System- a set of interacting parts forming a complex whole
Variable- something that can be changed and may be measured
Active annotation CFS: Earth's Geomagnetism
Accurately identifies the central idea from the primary source of evidence
Write any questions you may have in each paragraph
Circle any words you may not know.
Practice:
Earth’s Geomagnetism
If you’ve ever used a compass, you’ve seen that you can turn it in different directions and the magnetic needle inside rotates to point north again, as if it had a mind of its own. This small magnetic needle is actually pushed and pulled by powerful magnetic forces that envelop Earth. Our planet is surrounded
by a huge magnetic field that reaches from Earth’s core all the way into space.
Magnetic forces like those caused by Earth’s geomagnetic field may seem mysterious. These forces act on objects at a distance, and we can’t see or touch them. To help visualize magnetic forces, scientists model them using magnetic field lines. These scientific models help scientists predict and explain how magnetic forces work. In a model ofa single magnet, lines are drawn looping outward between opposite magnetic poles.
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Question 2
2.
What is the focus of the first 2 paragraphs? (summarize)
"The focus of the first two paragraphs is ... "
In a model with more than one magnet, the field lines are sometimes drawn connecting opposite poles on the magnets. These field lines help predict the direction of the forces pulling or pushing different magnets. A model showing field lines connecting the opposite poles of different magnets indicates that the magnets will be attracted together. A model showing two magnets that are not connected to each other by field lines indicates that the magnets will repel each other.
Compasses are helpful in determining which direction the magnetic field is going and where the field lines should be drawn. Field lines drawn to model Earth’s magnetic forces are based on the directions compass needles point at different places on Earth. Compass needles spin so that one end points to the north pole. This happens because each geomagnetic pole attracts the opposite pole of the compass at the same time it repels the like pole of the compass. These magnetic forces cause the compass needle to rotate until it points north.
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Question 3
3.
How do scientists model magnetic forces?
"Scientist model magnetic forces by using ... "
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Question 4
4.
In what direction do magnetic field lines travel around a magnet? (look at the image above)
You can see the effect of Earth’s magnetic field when you hold a compass in your hand— the needle points north, and knowing which way is north can help you find south, east, and west. Some animals can figure this out without looking at a compass. They have tiny bits of metal in their cells that act like tiny compass needles! These bits of metal rotate to point north, giving these animals a natural sense of which way is north. Animals like bees, bats, and some types of birds use this knowledge to find their way. Some use it for short distances, like bees that have flown away from their hives. Others, like snow geese, use it to migrate thousands of miles every year.
Earth acts like a giant bar magnet, with a north pole and a south pole that affect compass needles, but there isn’t actually a bar magnet in the center of Earth. Earth’s magnetic field is caused by the planet’s liquid iron core moving around. The process that creates a planet- wide magnetic field is called geomagnetism.
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Question 5
5.
What makes a compass point north?
CFS:
Describes the changes in a magnetic as it moves in a system
Accurately describes the relationship between magnetic orientation and movement of magnets in a system
"A compass needle points north because ... "
It may seem amazing that forces produced in the center of Earth could act on objects so far away, but Earth’s magnetic field actually reaches much farther than Earth’s surface. These forces are acting on Earth all the time, and we use them for everything from navigation to sorting recycling. So although you can’t see them, you interact with the forces of geomagnetism every day.
Exit Ticket:
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Question 6
6.
Draw how magnetic field lines look when magnets will attract? Repel? (use the image in the article question 4)