i-01-LBN-861773 8/24/04 9:55 AM Page i PhotoDisc i-01-LBN-861773 8/24/04 9:55 AM Page ii Electricity and Magnetism Iron filings cluster around the north and south poles of a bar magnet because of magnetic force.Magnetic force is exerted through a magnetic field, which is outlined by the iron filings.This field is caused by negatively charged electrons spinning in the atoms. Copyright ©2005 by The McGraw-Hill Companies,Inc.All rights reserved.Except as permitted under the United States Copyright Act,no part of this publication may be reproduced or distributed in any form or by any means,or stored in a database or retrieval system,without prior written permission of the publisher. The National Geographic features were designed and developed by the National Geographic Society’s Education Division.Copyright ©National Geographic Society.The name “National Geographic Society” and the Yellow Border Rectangle are trademarks of the Society,and their use,without prior written permission,is strictly prohibited. The “Science and Society”and the “Science and History”features that appear in this book were designed and developed by TIME School Publishing,a division of TIME Magazine.TIMEand the red border are trademarks of Time Inc.All rights reserved. Send all inquiries to: Glencoe/McGraw-Hill 8787 Orion Place Columbus,OH 43240-4027 ISBN:0-07-861773-1 Printed in the United States of America. 2 3 4 5 6 7 8 9 10 027/111 09 08 07 06 05 04 PhotoDisc i-01-LBN-861773 8/24/04 9:55 AM Page iii Authors Margaret K. Zorn Science Writer Education Division Yorktown,VA Washington,D.C. Dinah Zike Cathy Ezrailson Educational Consultant Science Department Head Dinah-Might Activities,Inc. Academy for Science and Health Professions San Antonio,TX Conroe,TX Series Consultants CONTENT READING ACTIVITY TESTERS Jack Cooper Barry Barto Nerma Coats Henderson Ennis High School Special Education Teacher Pickerington Lakeview Jr.High Ennis,TX John F.Kennedy Elementary School Manistee,MI Pickerington,OH Carl Zorn,PhD StaffScientist Rachel Swaters-Kissinger Mary Helen Mariscal-Cholka Jefferson Laboratory Science Teacher William D.Slider Middle School Newport News,VA John Boise Middle School El Paso,TX Warsaw,MO MATH Science Kit and Boreal SAFETY Laboratories Michael Hopper,DEng Tonawanda,NY Manager ofAircraft Certification Sandra West,PhD L-3 Communications Department ofBiology Greenville,TX Texas State University-San Marcos San Marcos,TX Series Reviewers Deidre Adams Anthony J.DiSipio,Jr. West Vigo Middle School 8th Grade Science West Terre Haute,IN Octorana Middle School Atglen,PA Karen Curry East Wake Middle School George Gabb Raleigh,NC Great Bridge Middle School Chesapeake Public Schools Chesapeake,VA N ◆ iii i-01-LBN-861773 8/24/04 9:55 AM Page iv Why do I need my science book? Before You Read Have you ever been in class and not understood all of what was ● Chapter Opener Science is occurring all around you, presented? Or, you understood and the opening photo of each chapter will preview the everything in class, but at home, science you will be learning about.The Chapter got stuck on how to answer a Preview will give you an idea of what you will be question? Maybe you just learning about,and you can try the Launch Lab to wondered when you were ever help get your brain headed in the right direction.The going to use this stuff? Foldables exercise is a fun way to keep you organized. ● Section Opener Chapters are divided into two to four These next few pages sections.The As You Read in the margin of the first are designed to help you page of each section will let you know what is most understand everything your important in the section.It is divided into four parts. science book can be used What You’ll Learn will tell you the major topics you for . . . besides a paperweight! will be covering.Why It’s Important will remind you why you are studying this in the first place! The Review Vocabulary word is a word you already know, either from your science studies or your prior knowl- edge.The New Vocabulary words are words that you need to learn to understand this section.These words will be in boldfaced print and highlighted in the section.Make a note to yourself to recognize these words as you are reading the section. (bkgd)John Evans, (inset)PhotoDisc i-01-LBN-861773 8/24/04 9:55 AM Page v Science Vocabulary Make the following Foldable to help you understand the vocabulary terms in this chapter. STEP 1 Folda vertical As You Read sheet of notebook paper from side to ● Headings Each section has a title side. in large red letters,and is further divided into blue titles and STEP 2 Cutalong every third line of only the small red titles at the begin- top layer to form tabs. nings of some paragraphs. To help you study,make an outline of the headings and subheadings. ● Margins In the margins of STEP 3 Labeleach tab with a vocabulary your text,you will find many helpful word from the chapter. resources.The Science Onlineexercises and Integrateactivities help you explore the topics you are studying.MiniLabsreinforce the sci- ence concepts you have learned. Build Vocabulary As you read the chapter, list the vocabulary words on the tabs. As you learn ● Building Skills You also will find an the definitions, write them under the tab for Applying Math or Applying Science activity each vocabulary word. in each chapter.This gives you extra prac- tice using your new knowledge,and helps prepare you for standardized tests. ● Student Resources At the end of the book you will find Student Resourcesto help you throughout your studies.These include Science,Technology,and Math Skill Hand- books,an English/Spanish Glossary,and an Look For... Index.Also,use your Foldablesas a resource. It will help you organize information,and review before a test. ● In Class Remember,you can always At the beginning of every section. ask your teacher to explain anything you don’t understand. N ◆ v (t)PhotoDisc, (b)John Evans i-01-LBN-861773 8/24/04 9:55 AM Page vi In Lab Working in the laboratory is one of the best ways to understand the con- cepts you are studying.Your book will be your guide through your laboratory experiences,and help you begin to think like a scientist.In it,you not only will find the steps necessary to follow the investigations,but you also will find helpful tips to make the most of your time. ● Each lab provides you with a Real-World Question to remind you that science is something you use every day,not just in class.This may lead to many more questions about how things happen in your world. ● Remember,experiments do not always produce the result you expect. Scientists have made many discoveries based on investigations with unex- pected results.You can try the experiment again to make sure your results were accurate,or perhaps form a new hypothesis to test. ● Keeping a Science Journal is how scientists keep accurate records of obser- vations and data.In your journal,you also can write any questions that may arise during your investigation.This is a great method of reminding yourself to find the answers later. L● oLMoauiknnic LhaF bLaos binrs .tsh.tae. rmt eavregriyn cohf aepatcehr. ● cThwapot eFru. ll-Period Labs in every ● ●●cEheXatndhTpdeeRt e omAWrf. oTyenorbyus stra irbttae oHtoiwookm.inthse .l aLabbosraatto trhye vi ◆ N (l)John Evans, (r)Geoff Butler i-01-LBN-861773 8/24/04 9:55 AM Page vii Before a Test Admit it! You don’t like to take tests! However,there are ways to review that make them less painful.Your book will help you be more successful taking tests if you use the resources provided to you. ● Review all of the New Vocabulary words and be sure you understand their definitions. ● Review the notes you’ve taken on your Foldables, in class, and in lab.Write down any question that you still need answered. ● Review the Summaries and Self Check questions at the end of each section. ● Study the concepts presented in the chapter by reading the Study Guide and answering the questions in the Chapter Review. Look For... ● Reading Checksand caption questionsthroughout the text. ● the Summariesand Self Check questionsat the end of each section. ● the Study Guideand Review at the end of each chapter. ● the Standardized Test Practice after each chapter. N ◆ vii (l)John Evans, (r)PhotoDisc i-01-LBN-861773 8/24/04 9:55 AM Page viii Let’s Get Started To help you find the information you need quickly, use the Scavenger Hunt below to learn where things are located in Chapter 1. What is the title of this chapter? What will you learn in Section 1? Sometimes you may ask,“Why am I learning this?”State a reason why the concepts from Section 2 are important. What is the main topic presented in Section 2? How many reading checks are in Section 1? What is the Web address where you can find extra information? What is the main heading above the sixth paragraph in Section 2? There is an integration with another subject mentioned in one of the margins of the chapter.What subject is it? List the new vocabulary words presented in Section 2. List the safety symbols presented in the first Lab. Where would you find a Self Check to be sure you understand the section? Suppose you’re doing the Self Check and you have a question about concept mapping.Where could you find help? On what pages are the Chapter Study Guide and Chapter Review? Look in the Table of Contents to find out on which page Section 2 of the chapter begins. You complete the Chapter Review to study for your chapter test. Where could you find another quiz for more practice? viii ◆ N PhotoDisc i-01-LBN-861773 8/24/04 9:55 AM Page ix Teacher Advisory Board The Teacher Advisory Board gave the editorial staff and design team feedback on the content and design of the Student Edition.They provided valuable input in the devel- opment of the 2005 edition of Glencoe Science. John Gonzales Marie Renner Rubidel Peoples Challenger Middle School Diley Middle School Meacham Middle School Tucson,AZ Pickerington,OH Fort Worth,TX Rachel Shively Nelson Farrier Kristi Ramsey Aptakisic Jr.High School Hamlin Middle School Navasota Jr.High School Buffalo Grove,IL Springfield,OR Navasota,TX Roger Pratt JeffRemington Manistique High School Palmyra Middle School Manistique,MI Palmyra,PA Kirtina Hile Erin Peters Northmor Jr.High/High School Williamsburg Middle School Galion,OH Arlington,VA Student Advisory Board The Student Advisory Board gave the editorial staff and design team feedback on the design of the Student Edition.We thank these students for their hard work and creative suggestions in making the 2005 edition of Glencoe Science student friendly. Jack Andrews Addison Owen Reynoldsburg Jr.High School Davis Middle School Reynoldsburg,OH Dublin,OH Peter Arnold Teriana Patrick Hastings Middle School Eastmoor Middle School Upper Arlington,OH Columbus,OH Emily Barbe Ashley Ruz Perry Middle School Karrer Middle School Worthington,OH Dublin,OH Kirsty Bateman Hilliard Heritage Middle School Hilliard,OH Andre Brown Spanish Emersion Academy Columbus,OH Chris Dundon Heritage Middle School Westerville,OH The Glencoe middle school science Student Ryan Manafee Monroe Middle School Advisory Board taking a timeout at COSI, Columbus,OH a science museum in Columbus, Ohio. N ◆ ix Aaron Haupt Photography i-01-LBN-861773 8/24/04 9:55 AM Page x Contents Nature of Science: s nt Electricity and Magnetism—2 e t n o C Electricity—6 In each chapter, look for these opportunities for Section 1 Electric Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 review and assessment: Section 2 Electric Current . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 • Reading Checks Section 3 Electric Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 • Caption Questions • Section Review Lab Current in a Parallel Circuit . . . . . . . . . . . . . .27 • Chapter Study Guide Lab A Model for Voltage and Current . . . . . . . . . .28 • Chapter Review • Standardized Test Practice • Online practice at bookn.msscience.com Magnetism—36 Section 1 What is magnetism? . . . . . . . . . . . . . . . . . . . . . . . .38 Lab Make a Compass . . . . . . . . . . . . . . . . . . . . . . .44 Section 2 Electricity and Magnetism . . . . . . . . . . . . . . . . . . .45 Lab How does an electric motor work? . . . . . . . .56 x ◆ N V.C.L./Getty Images