Understanding Electromagnetic Waves and Radio Technology, Study notes of Classical Physics

Download Understanding Electromagnetic Waves and Radio Technology and more Study notes Classical Physics in PDF only on Docsity! 13.1 Radios and Electromagnetic waves New ideas for today: •Electrical resonators (tank circuits) •Electromagnetic waves (light) •How FM and AM radio works What do all radios have in common? Antennas! • Charges move in the transmitting antenna • Those charges exert forces on charges in receiving antenna • Charges in the receiving antenna move Tank circuits are used to turn small amounts of sloshing charges into large amounts of sloshing charges! Tank circuits are all around you: • Cell phone • Any watch with a battery / electronic clock • Computers… Tank circuit Capacitor Just two plates of metal •Stores charges •Stores energy – it takes work to separate charges that attract! Inductor Just a loop of wire Moving charges (current) store energy in magnetic field Tank circuit Electric energy Electric energy Magnetic energy Magnetic energy This is just like a pendulum! Potential energy Kinetic energy Potential energy Ever wonder how a traffic light “knows” that a car is waiting? That loop of wire is part of a tank circuit…and your car changes its inductance! Alice and Bob each use a hand- cranked generator to charge a capacitor. Who has done more work? + + + - - - + + ++++++ - - - - - - - - (A) (B) Clicker question