Lecture 7
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What is the difference between Oersted’s and Faraday’s theories on electricity and magnetism?
Oersted: magnetic effects arise from electricity. Faraday: electrical effects arise from magnetism.
How does an ammeter work?
A battery is put inside a coil to generate electricity that will be detected with a needle. Faraday found that one ammeter with a battery when placed next to one without would cause the second one to detect electricity called electromagnetic induction
What does the ammeter experiment prove?
Electrical fields and electrical currents can be produced by changing magnetic fields
What is the unifying theory of electromagnetism?
Electricity and magnetism are not distinct phenomena at all, but are simply different manifestations of one underlying fundamental entity, the electromagnetic force
What did James Clerk Maxwell realize?
Many independent observations about electricity and magnetism constitute a complete description of electromagnetism, allowing him to come up with equations
What are Maxwell’s equations?
• Coulomb’s law: like charges repel and unlike charges attract • There are no magnetic monopoles in nature • Magnetic phenomena can be produced by electrical effects • Electrical phenomena can be produced by magnetic effects
What are waves?
A wave is a traveling disturbance, they have the ability to transfer energy without transferring mass
What is electromagnetic waves/radiation?
Whenever an electrically charged object is accelerated, waves of energy are propagated through space and travel at the speed of light or 300,000 km/sec
What are examples of waves?
gamma rays, x-rays, microwaves, radio waves, and visible light
What is wavelength?
The distance between crests or the highest points of adjacent waves
What is frequency?
The number of crests that go by a given point every second. If you have a frequency of 1 Hertz, then 1 crest is sent up and down every second. If you have a frequency of 10, 1 wave goes up and down 10 times in a second
What is a period?
The time between adjacent waves. 1/frequency
What is velocity?
The speed and direction of the wave crest itself
What is amplitude?
Height of the wave crests above the undisturbed position
What is the equation of velocity?
velocity in meters/second = wavelength in meters x frequency in hertz
What is the difference between a transverse and a longitudinal wave?
A transverse wave move is perpendicular to wave direction, when longitudinal is motion in the same direction as waves
Electromagnetic waves are made up of?
electrical and magnetic field that fluctuate together, that once started will go forever
How does the electromagnetic wave move?
Electrical and magnetic fields are arranged at right angles to each other, perpendicular to the direction the wave is moving. The wave keeps renewing itself allowing it to trasnfer energy and continue traveling
Wavelength and frequency are?
Inversely related to each other where when frequency goes up wavelength goes down, when frequency goes down wavelength goes up.
What do red colors look like on the electromagnetic spectrum?
Red colors have a lower frequency and higher wavelength causing there to be lower energy as frequency and energy are directly proportional.
How do red colors look on the electromagnetic spectrum?
They have shorter wavelengths, higher frequencies and higher energy
When are electromagnetic waves generated?
Any time a charged object is accelerated. Wavelength = velocity/frequency so if a wave moves once every second the wavelength will be 300,000/1 like between the earth and the moon, but if it has a frequency of 300,000 it will have a wavelength of 1 km making it happen more often