1. Magnets And Magnetic Fields

2. Review Just like Electricity, magnets work in FIELDS. Fields are drawn with VECTORS Review: Up, Down, Left and Right

3. Review With Magnetism, we will need to look at vectors in 3-D. How do we draw a vector arrow going into the page? What would a real arrow look like going away from us?

4. Review Kind of like this: So we draw it like this:

5. Review What would a real arrow look like coming directly toward you?

6. Review Like this: So we draw it like this:

7. Magnetism Magnetism works in a field, like Electricity. We use B for the magnetic field variable.

8. Magnetism Magnets work a lot like a PROTON and an ELECTRON. Imagine a bar of metal with all the PROTONS on one end and the ELECTRONS on the other. + + + + + + + + + - - -

9. Magnetism The left side is positively charged, right side negatively charged and the field would look like this: + + + + + + + + + - - -

10. Magnetism If this were a magnet, there would be a North and South pole instead. Field looks the SAME + + + + + + + + + - - - NS

11. Electricity and Magnetism Electricity and Magnetism are “chained” together.

12. E & M Whenever you have an ELECTRIC CURRENT, there is a MAGNETIC FIELD too, and vice versa. One is always quite larger than the other.

13. E & M Ever had a power cord to close to a TV screen? The distortion is from the Magnet Field around the cord.

14. E & M Example: Current vs. Magnetic Field in a power cord LARGE current SMALL magnetic field

15. E & M Other Examples: High Voltage Power lines Big VSmall B MRI Machine Huge VMedium B Refrigerator Magnet Medium BTiny V

16. Magnetic Fields How do we know what the Magnetic Field looks like around a wire with current in it?

17. Magnetic Fields There are some rules to help us. They are called Right Hand Rules. Step 1: USE YOUR RIGHT HAND!!

18. Right Hand Rule #1 What does a magnetic field, B, look like around a wire? Grab some wire with your RIGHT hand I

19. Right Hand Rule #1 Make sure your thumb is going in the same direction as the current is! I

20. Right Hand Rule #1 Your 4 fingers are lined up with the magnetic field. It goes in a circle around the wire. I

21. Right Hand Rule #1 A field diagram would look like this: (Remember the vector arrows) Front Top Bottom I I II

22. Right Hand Rule #2 What happens if we play with an electric cord in a magnetic field that was already there?

23. Right Hand Rule #2 We’ll set it up like this: I N (+) S (-)

24. Right Hand Rule #2 Even without the wire, the magnets have a field already: N (+) S (-) B

25. Right Hand Rule #2 So what happens when the power is turned on? The wire starts moving! But what direction?? N (+) S (-) B I

26. Right Hand Rule #2 Right Hand Rule #2 tells us in what direction the wire will be pushed… N (+) S (-) B I

27. Right Hand Rule #2 STEP 1: USE RIGHT HAND!!! N (+) S (-) B I

28. Right Hand Rule #2 Index Finger points with B. N (+) S (-) B I

29. Right Hand Rule #2 Other three point with I N (+) S (-) B I

30. Right Hand Rule #2 Stick your thumb out. That’s the direction of the force (the way the wire will go). N (+) S (-) B I

31. Practice The 2 nd Right Hand rule will take some getting used to: #1- Index finger with B #2- Other three with I 3#- Thumb gives you the answer