9/3/2019 Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine tomburbine@astro.umass.edu

Magnetic Poles Like poles repel Opposite poles attract North pole South pole

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

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

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

Magnetic Field The region of magnetic influence around a magnetic pole or a moving charged particle Field of force

Motion of electric charges Electron spinning Electron revolution around the protons

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

Metals Materials such as iron, nickel, and cobalt have electrons whose spins do not cancel out Iron has four paired electrons that can have the same spin

Magnetic domains Clusters of atoms line up with one another

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

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

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

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

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

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Any Questions?