Introduction to Physical Science Monday Wednesday Thursday Tom

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

• http: //video. google. com/videoplay? docid=390246 6783636795302#

Any Questions?