Activity B1-WA due by 4 pm Friday 03/28 Chapter 5 Mallard HW quiz – Due by 12 AM Thursday 03/27 Chapter 5 quiz in class on Thursday 03/27 Tuesday, March 25 Spring 2008

Electricity and Magnetism Chapter 5 Great Idea: Electricity and magnetism are two different aspects of one force—the electromagnetic force

Batteries and Electrical Current Electrical current –Flow of charged particles –Symbol: I –Units: Coulombs/second (C/s) Voltage –the difference in electrical charge between two points in a circuit (electrical “pressure”) –Symbol: V –Units: volts (V) Battery –Converts chemical energy to kinetic energy (energy of flowing charges)

Electric Circuits Electric circuit –Unbroken path of material carrying electricity Circuit components 1. Source 2. Closed path 3. Device to use electrical energy Ohm’s Law –Current is directly proportional to voltage V and inversely proportional to resistance R –In symbols: I = V / R Electric Power: P = I × V

Magnetic Effects from Electricity Oersted –Magnetic field created by motion of electrical charges Magnetic Monopole –Does not exist –Magnetism is related to arrangement of electrical charges in atoms Electromagnet

Electric Motors & Magnetism

Electrical Effects from Magnetism Faraday –Electromagnetic induction –Electrical fields and currents can be produced by changing magnetic fields Electric Generator

Maxwell’s Equations Coulomb’s Law No magnetic monopoles Magnetic phenomena produced by electrical effects Electrical phenomena produced by magnetic effects

Waves & Electromagnetic Radiation Chapter 6 Great Idea: Whenever an electrically charged object is accelerated, it produces electromagnetic radiation—waves of energy that travel at the speed of light

Waves A wave is a traveling disturbance that transports energy from one place to another without transporting matter across the intervening distance.

Oscillation – back-and-forth motion about an equilibrium position Cycle – one complete oscillation or repetition of a periodic motion Period, T – the length of time required for one cycle Frequency, f – number of cycles that occur during a unit of time f = 1 / T Amplitude – distance traveled above or below equilibrium position Simple Oscillations

Properties of Periodic Waves Speed of wave: v = f f v time between wave crests A periodic wave is a wave made of a series of pulses separated by equal time intervals.

Sample Exercise Suppose that water waves have a wavelength of 1.4 m and a period of 0.8 s. What is the frequency of these waves? What is the velocity of these waves?

Sample Exercise A wave on a rope is shown in the diagram. a. What is the wavelength of this wave? b. If the speed of the wave is 6 m/s, what is its frequency?

Longitudinal wave – motion in same direction as wave Transverse wave – motion perpendicular to wave direction Two Basic Wave Types

A sound wave is a periodic longitudinal wave of pressure variations propagating through a medium. Sound Waves

Sound Waves The shapes of instruments and the materials they’re made of influence the pitch and timbre of the sound they create... Pitch of sound is determined by its frequency and speed High frequency = high pitch; low frequency = low pitch

Sound Waves L = ½ Sound waves travel at about 340 m/s (≈ 760 mi/h) in air

Doppler Effect Apparent shift in frequency of a wave emitted from or received by a moving source

–Constructive Interference Add together –Destructive Interference Cancellation Wave Interference wave addition

Electromagnetic Waves Self-propagating radiant energy Energy transferred by oscillating electric and magnetic fields created by accelerated charges Electromagnetic waves continue through internal mechanisms and transfer energy as they travel; they do not require a medium to travel.

Speed of Light Higher frequency visible light = blue color Lower frequency visible light = red color c = 3 × 10 8 m/s = 186,000 mi/s v = f = c All electromagnetic waves travel at the same speed Energy of wave: E = hf ( h is Planck’s constant = × m 2 ·kg/s)

Interaction of EM Waves & Matter Transmission: wave passes through matter refraction & dispersion Absorption: wave & energy are absorbed Scattering: wave & energy absorbed and reemitted diffuse scattering reflection

The Blue Sky – Light Scattering Molecules in the air preferentially scatter high frequency blue light waves – sky appears blue when viewed away from direct sunlight Sky appears white around the Sun – yellow/orange/red when light traverses long distances through the atmosphere BlueSky/blue_sky.html

Electromagnetic Waves & the Doppler Effect Apparent shift in frequency of a wave emitted from or received by a moving source Higher frequency light: “blueshifted” Lower frequency light: “redshifted”