24 Magnetic Fields BIGIDEA Write the Big Idea for this chapter.

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1 24 Magnetic Fields BIGIDEA Write the Big Idea for this chapter. Use the What I Know column to list the things you know about the Big Idea. Then list the questions you have about the Big Idea in the What I Want to Find Out column. As you read the chapter, fill in the What I Learned column. K What I Know W What I Want to Find Out L What I Learned 355

2 24 Magnetic Fields 1 Understanding Magnetism 5(A), 5(D) MAINIDEA Write the Main Idea for this section. REVIEW VOCABULARY conventional current Recall and write the definition of the Review Vocabulary term. conventional current NEW VOCABULARY polarized domain magnetic field magnetic flux Use your book to define each term. polarized domain electromagnetic force solenoid electromagnet magnetic field magnetic flux electromagnetic force solenoid electromagnet 356

3 Student Edition, pp List four examples of objects you use frequently that rely on magnets to operate. Explain why the arrow on a compass points to geographical north. Explain What happens to the poles of a magnet if you cut it in half? Draw Suppose you move a strong magnet so that it touches a piece of nickel wiring. In the top box, sketch arrows representing the domains in the wire before it touches the magnet. In the bottom box, sketch the domains after the wire has been touching the magnet for several hours. Before the nickel wire touches the magnet After the nickel wire touches the magnet 357

4 Student Edition, pp Describe how the ocean floor records the Earth s magnetic field. GET IT? Compare How are magnetic fields like electric fields? Draw Sketch a diagram of magnetic field lines around a bar magnet. Describe what the magnetic field lines would look like for a magnet exerting a force on a nearby ferromagnetic material. Also describe the behavior of the domains in the ferromagnetic material. 358

5 Student Edition, pp Describe the relationship between the compass needle and the currentcarrying wire in Oersted s experiments. Explain the right-hand rule you can use to determine the direction of a magnetic field around a current-carrying wire. List four ways to increase the strength of an electric field produced by a solenoid. Explain the right-hand rule you can use to determine the north pole of a solenoid. Describe how a solenoid records information in a computer. 359

6 SUMMARIZE How does the MAINIDEA for this section relate to the chapter s BIGIDEA? REVIEW IT! 10. MAINIDEA Explain how to construct an electromagnet. 11. Magnetic Fields What two things about a magnetic field can magnetic field lines represent? 12. Magnetic Forces Identify some magnetic forces around you. How could you demonstrate the effects of those forces? 13. Magnetic Fields Where on a bar magnet is the magnetic field the strongest? 360

7 14. Magnetic Fields Two current-carrying wires are close to and parallel to each other and have currents with the same magnitude. If the two currents were in the same direction, how would the magnetic fields of the wires be affected? How would the fields be affected if the two currents were in opposite directions? 15. Direction of Field Describe how to use a right-hand rule to determine the direction of a magnetic field around a straight, current-carrying wire. 16. Electromagnets A glass sheet with iron filings sprinkled on it is placed over an active electromagnet. The iron filings produce a pattern. If this scenario were repeated with the direction of current reversed, what observable differences would result? Explain. 17. Magnetic Domains Explain what happens to the domains of a temporary magnet when the temporary magnet is removed from a magnetic field. 18. Critical Thinking Imagine a toy containing two parallel, horizontal metal rods, one above the other. The top rod is free to move up and down. a. The top rod floats above the lower rod. When the top rod s direction is reversed, however, it falls down onto the lower rod. Explain how the rods could behave in this way. b. Assume the toy s top rod was lost and another rod replaced it. The new rod is attracted to the bottom rod no matter its orientation. What type of material is in the replacement rod? 361