1. Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine tomburbine@astro.umass.edu

3. Magnetic Poles Like poles repel Opposite poles attract North-seeking pole points northward South-seeking pole points southward

4. Magnetic Force 1) Between magnets, it is the attraction of unlike magnetic poles and the repulsion of like magnetic poles 2) Between a magnetic field and moving charge, it is the deflecting force due to the motion of the charge

5. Difference between magnetic poles and electron charges Electric charges can be isolated –Protons and electrons can exist separately Magnetic poles cannot –North magnetic poles can’t exist without south poles

6. If you break a magnet in half, each half will act as a magnet If you break that piece in half, you will then have four magnets This suggests that the atoms themselves are magnets

7. Magnetic Field The region of magnetic influence around a magnetic pole or a moving charged particle Direction of the field, by convention, is from the north pole to the south pole

8. Motion of electric charges Electron spinning Electron revolution around the protons

9. Electron spinning An electron spinning creates a magnetic field A pair of electrons spinning in the same direction creates a stronger magnet A pair of electrons spinning in the opposite direction work against each other

11. Metals Materials such as iron, nickel, and cobalt have electrons whose spins do not cancel out

14. Magnetic domains Clusters of atoms line up with one another

15. Permanent Magnet Place a piece of iron (or a similarly magnetized material) in a strong magnetic field

16. Moving charge produces a magnetic field A current of charge produces a magnetic field

17. Electromagnetic Induction Electric current can be produced in a wire simply by moving a magnet into or out of a coil of wire A voltage is induced by the relative motion between a wire and the magnetic field

19. Faraday’s Law The induced voltage of a coil is proportional to the number of loops multiplied by the rate at which the magnetic field changes within those loops

20. More practical to move the coil then move the magnet Generator has a rotating coil in a stationary magnetic field Converts mechanical energy into electrical energy

21. Any Questions?