Unit 4 - Topic 6 Flashcards
Portable power uses
Batteries
Most electricity comes from conversion of
Mechanical energy
Mechanical energy associated w/
Examples
Any system w/ moving parts
Rotating windmill
Spinning turbines in thermo-electric, nuclear, geothermal power plants
Moving water of rivers/tides
Electric generator + surprising relationship
A device that converts mechanical energy into electric energy
Depends on relationship between electricity and magnetism
Hans Christian Oersted/1820 observations
Danish physicist
Relationship between electricity and magnetism
Compass needle turned when near wire carrying electric current
Amount of deflection depended on amount of current
When current reversed, needle moved in opp direction
When current interrupted, magnetic effects ceased
HCO fun fact
Wanted to show no relationship between electricity and magnetism
Proved himself wrong
Electromagnet
Strong temporary magnet, created by inserting a sift iron cure into a coil of wire and then passing a current through the wire
What happens in electromagnet when current passed through wire
One end of core becomes magnetic north pole and other the south pole
Variables to increase magnet strength
Wrap more coils around core
Increasing current passed through
Changing material of core
If direction of current is reversed …
If the current is turned off …
The polarity of the magnet is reversed
The iron core loses its magnetic properties
What’s stronger iron vs metals, woods, or plastics
Iron
Michael Faraday
Crediting w/ discovering basic principles of electromagnetism
Experiments formed basis of modern electromagnetic tech and electro chemistry
Introduced terms: ion, electrode, cathode, anode to science
Invented idea of lines of magnetic force
Unit for stored electric charge
Farad
Named after Faraday
Components of simple electromagnet
Electric power source
Wire
Soft iron bar
Individual atoms have
North and south pole
Magnetic domains in magnetized and unmagnetized
Atoms group together in which all north poles face same way
Or
Atoms have domains randomly arranged so magnetic effects cancel out
Domains in magnet/electromagnet
Aligned
Resulting magnetic effects strengthened
Why iron is effective core
Domains line up easily
Good in electromagnets
Wire and magnet statement
Relative motion between a wire and magnet causes a current to flow in a circuit connected to the wire.
Voltage is “induced” when there is relative motion between the two
When wire connected to a circuit, “induced current” flows
AC vs DC generator
Alternating current vs direct current
Common AC generator
Coil of wire rotates inside stationary magnet
Coil rotated by external force
As wires in coil rotate, electrons begin to move in one direction
After one half revolution, current changes direction as electrons move other way
Current changes direction twice in one revolution hence name alternating current
Hertz
Used to describe full waves each second for alternating current
Current changing direction 120 times per second would equal 60 Hertz or cycle AC
Alternators
Generators that produce alternating current
Why power plants produce AC
Relatively easy to increase or decrease voltage of
In order to travel long distances voltage must be increased then decreased for usage
