1. ES Lesson 5 What is a magnet? What is a magnetic force field? What is an electromagnet? What is a magnetic coil? © 2012 C. Rightmyer, Licensed under The MIT OSI License, 20 July 2012

2. (1600) William Gilbert writes “De magnete” Physician to Queen Elizabeth I. Studied electric attraction, electric force, and magnetism over his entire lifetime. Recorded his research and experiments in a 6-book treatis on these subjects. After experiments with a terrella (spherical magnet), he proposed that the earth is a giant magnet. Coined term “electricity” from the Greek word for amber. Guessed correctly that iron can be temporarily magnetized by induction.

3. What is a magnet? Electricity and Magnetism, Gareth Stevens Publishing, Steve Parker, 2007

4. ES project 5-1. Magnetic attraction and repelling [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

5. The earth itself acts like a magnet [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

6. ES project 5-2. Make a compass Push the magnetised sewing needle lenthwise through the cork. Place the cork into a bowl of water. The cork will rotate to point towards the north. [Science Action Labs TLC10207 Electricity and Magnetism, Teaching and Learning Co,, Edward Shevick,, 2000]

7. ES demo 5-3. A bar magnet dipped in iron filings [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

8. ES demo 5-4. Magnetic force field about a bar magnet [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

9. ES demo 5-5. What happens to a bar magnet if broken into several pieces? [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

10. ES demo 5-6. Attractive force between opposite poles [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

11. ES demo 5-7. Repelling force between same type pole. [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

12. ES demo 5-8. Magnetic induction in action [Adapted from an idea presented at http://www.phy6.org/earthmag/inducemg.htm]

13. ES demo 5-9. Use a compass to observe magnetic field direction. [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960] Strong Weak

14. ES demo 5-10. Hans Christian Orsted’s accidental discovery + 9 volts BE demo 1-11

15. A stronger magnetic field is generated when the wire is formed into a coil Adapted from Make: Electronics, O’reilly [Publishing], Charles Platt, 2009 Electromagnetic field induced by current + + - Magnetic field adds in center of circular coil L (in microHenrys) = (approximately) D ^2 x N ^2 / [(18xD) + (40xW)]

16. The magnetic field in a conducting coil is like that of a cylindrical permanent magnet. Electricity and Magnetism, Gareth Stevens Publishing, Steve Parker, 2007

17. ES project 5-11. Make an electromagnet by winding a coil around a steel nail. [Teaching Electricity, Scholastic Professional Books, Steve Tomecek, 1999] 3 volts BE demo 1-12

18. L3 Background slides

19. Compressing the coil generates a magnetic field much like a button magnet. [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960]

20. Making your own compass [Science Action Labs TLC10207 Electricity and Magnetism, Teaching and Learning Co,, Edward Shevick,, 2000]