Mimi

What You’ll Learn

• You will assign forces of attraction or repulsion between magnetic poles. • You will relate magnetism to electric charge and electricity. • You will describe how electromagnetism can be harnessed for practical applications.

Why It’s Important

Magnetism is the basis for many technologies. Information on the hard drive of a computer is stored as a magnetic pattern. Atom Smashers An accelerator tube, such as the one pictured, is surrounded by superconducting magnets. There is no magnetic field at the center of the tube where high-energy particles travel. If the particles stray from the center, they receive a magnetic push to keep them there.

Think About This

How do forces applied by magnets cause particles to accelerate? Can any particle be accelerated?

physicspp.com

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Fermilab/Peter Arnold, Inc.

In which direction do magnetic fields act?

Question What would be the direction of force on a magnetized object in a magnetic field? Procedure 1. Place a bar magnet horizontally in front of you so that the north pole faces left. 2. Place a second bar magnet horizontally next to, and 5.0 cm away from the first (you should be able to place the compass between the magnets). The north pole also should be facing the left. 3. Draw your setup on a sheet of paper. Be sure to label the poles. 4. Place a compass by the two magnets. Draw the direction the arrow is pointing. 5. Continue to move the compass to other positions, each time drawing the direction it points until you have drawn 15–20 arrows. 6. Repeat steps 3–5, this time with the two north poles facing each other. Analysis What did the red end of the compass needle typically point toward? Away from? Why might some of the arrows not point to either location stated in question 1? Critical Thinking What you have diagrammed with your arrows is called a magnetic field. Recall what a gravitational field and an electric field are, and define magnetic field.

24.1 Magnets: Permanent and...