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Magnets

Magnets. And Magnetic Fields. Review. Just like Electricity, magnets work in FIELDS. Fields are drawn with VECTORS Review: Up, Down, Left and Right. Review. With Magnetism, we will need to look at vectors in 3-D. How do we draw a vector arrow going into the page?

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Magnets

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  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 + + + + + + + + + • - - • - - • - - N S

  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 V Small B • MRI Machine Huge V Medium 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) FrontTopBottom I I I I

  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: N (+) I S (-)

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

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

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

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

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

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

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

  31. Practice • The 2nd 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

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