radio 1 radio. radio 2 observations about radio transmit sound long distances without wires transmit...
TRANSCRIPT
Radio 1
RadioRadio
Radio 2
Observations about Observations about RadioRadio
Transmit sound long distances without Transmit sound long distances without wireswires
Involve antennasInvolve antennas Seem to involve electricity and Seem to involve electricity and
magnetismmagnetism Reception depends on antenna Reception depends on antenna
positioningpositioning Reception weakens with distanceReception weakens with distance Two styles of radio: AM and FMTwo styles of radio: AM and FM
Radio 3
3 Questions about Radio3 Questions about Radio
How can a radio wave exist?How can a radio wave exist? How is a radio wave emitted and How is a radio wave emitted and
received?received? How can a radio wave represent How can a radio wave represent
sound?sound?
Radio 4
Question 1Question 1
How can a radio wave exist?How can a radio wave exist? What is an electromagnetic wave What is an electromagnetic wave
anyway?anyway? How can an electric field exist without How can an electric field exist without
charge?charge? How can a magnetic field exist without How can a magnetic field exist without
pole?pole?
Radio 5
Electromagnetic WavesElectromagnetic Waves
Radio waves are a type of Radio waves are a type of electromagnetic waveelectromagnetic wave a structure in space consisting only of an a structure in space consisting only of an
electric field and a magnetic fieldelectric field and a magnetic field Electromagnetic waves areElectromagnetic waves are
emitted or received by charge or poleemitted or received by charge or pole but are self-sustaining while traveling in but are self-sustaining while traveling in
vacuum.vacuum. Their electric and magnetic fields create Their electric and magnetic fields create
one anotherone another
Radio 6
Electromagnetism Electromagnetism (Version (Version 3)3)
Magnetic fields are produced byMagnetic fields are produced by magnetic poles (but free poles don’t magnetic poles (but free poles don’t
seem to exist),seem to exist), moving electric charges,moving electric charges, and changing electric fieldsand changing electric fields..
Electric fields are produced byElectric fields are produced by electric charges,electric charges, moving magnetic poles,moving magnetic poles, and changing magnetic fields.and changing magnetic fields.
Radio 7
Structure of a Radio Structure of a Radio WaveWave
Electric field is perpendicular to Electric field is perpendicular to magnetic fieldmagnetic field
Changing electric fieldChanging electric fieldcreates magnetic fieldcreates magnetic field
Changing magnetic fieldChanging magnetic fieldcreates electric fieldcreates electric field
Polarization of the wavePolarization of the waveis associated with theis associated with thewave’s electric fieldwave’s electric field
Radio 8
Question 2Question 2
How is a radio wave emitted and How is a radio wave emitted and received?received?
Radio 9
Launching a Radio WaveLaunching a Radio Wave
Accelerating charge emits Accelerating charge emits electromagnetic waveselectromagnetic waves
The more charge and the harder it The more charge and the harder it accelerates, the stronger the resulting accelerates, the stronger the resulting electromagnetic waveelectromagnetic wave
Radio stations need to emit strong wavesRadio stations need to emit strong waves so they move large amounts of chargeso they move large amounts of charge with the help of resonant devices: tank with the help of resonant devices: tank
circuitscircuits
Radio 10
A Tank CircuitA Tank Circuit
is a harmonic oscillator for charge and is a harmonic oscillator for charge and currentcurrent
Charge flows regularly back and forth Charge flows regularly back and forth fromfromone capacitor plate to the other, through one capacitor plate to the other, through the inductor.the inductor.
Its total energy shiftsIts total energy shiftsback and forth betweenback and forth betweenits inductor andits inductor andits capacitor.its capacitor.
Radio 11
Tank Circuit OscillationTank Circuit Oscillation
The frequency of the tankThe frequency of the tankcircuit is determined only by itscircuit is determined only by itsinductance and its capacitance.inductance and its capacitance.
It can store a great deal of energyIt can store a great deal of energyand have an enormous amountand have an enormous amountof charge moving through it.of charge moving through it.
Tank circuits come in manyTank circuits come in manyshapes, including straight lines!shapes, including straight lines!
Radio 12
Tank Circuits in RadioTank Circuits in Radio
Tanks build up energy at a specific Tanks build up energy at a specific frequencyfrequency
Two tanks help radios Two tanks help radios emitemit radio radio waveswaves The first tank circuit feeds the antennaThe first tank circuit feeds the antenna The second tank circuit is the antennaThe second tank circuit is the antenna
Two similar tanks help radios Two similar tanks help radios detectdetect radio wavesradio waves
Radio 13
Emitting Radio Waves Emitting Radio Waves (Part 1)(Part 1)
A transmitter uses a tank circuit to A transmitter uses a tank circuit to “slosh” charge up and down its “slosh” charge up and down its antenna,antenna,which acts as a second tank.which acts as a second tank.
A receiver uses a tank circuit toA receiver uses a tank circuit todetect charge “sloshing” on itsdetect charge “sloshing” on itstank-circuit antenna.tank-circuit antenna.
Transmitter antenna chargeTransmitter antenna chargeaffects receiver antenna chargeaffects receiver antenna charge
Antenna orientations matter!Antenna orientations matter!
Radio 14
Emitting Radio Waves Emitting Radio Waves (Part 2)(Part 2)
Accelerating charge emits radio wavesAccelerating charge emits radio waves Charge produces electric fieldCharge produces electric field Current produces magnetic fieldCurrent produces magnetic field Changing current produces changing Changing current produces changing
magnetic field, produces changing magnetic field, produces changing electric field, prod…electric field, prod…
A radio wave consists only of an A radio wave consists only of an electric and magnetic fieldelectric and magnetic field
A radio wave travels through empty A radio wave travels through empty space at the speed of lightspace at the speed of light
Radio 15
Question 3Question 3
How can a radio wave represent How can a radio wave represent sound?sound?
Radio 16
AM ModulationAM Modulation
Information can be encoded as a Information can be encoded as a fluctuating fluctuating amplitudeamplitude of the radio of the radio wavewave
The air pressure variationsThe air pressure variationsthat are sound causethat are sound causechanges in the amount ofchanges in the amount ofcharge moving on thecharge moving on theantennaantenna
Radio 17
FM ModulationFM Modulation
Information can be encoded as a Information can be encoded as a fluctuating fluctuating frequencyfrequency of the radio of the radio wavewave
The air pressure variationsThe air pressure variationsthat are sound causethat are sound causeslight shifts in theslight shifts in thefrequency of chargefrequency of chargemotion on the antennamotion on the antenna
Radio 18
Summary about RadioSummary about Radio
Radio waves are emitted by charge Radio waves are emitted by charge accelerating on a transmitting antennaaccelerating on a transmitting antenna
Radio waves are detected when they Radio waves are detected when they cause charge to accelerate on a receiving cause charge to accelerate on a receiving antennaantenna
Radio waves consist only of self-sustaining Radio waves consist only of self-sustaining electric and magnetic fieldselectric and magnetic fields
Radio waves can represent sound Radio waves can represent sound information as variations in amplitude or information as variations in amplitude or frequencyfrequency