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118 Cards in this Set
- Front
- Back
the flow of electrons from one place to another
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current electricity
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two types of electricity
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currents, static
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electricity that flows in only one direction
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direct current (DC)
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electricity that constantly reverses the direction it flows
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alternating current (AC)
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device that converts AC to CD
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rectifier
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why electrons flow
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because of the attraction and repulsion of electric charges
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the force of electron current flow
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voltage
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other names for voltage
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electric potential or electromotive force
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unit of voltage
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volt
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instrument used to measure voltage
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voltmeter
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the rate of electric flow
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current
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unit of current
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ampere
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energy used per unit time
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power
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unit of power
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watt
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formula for power
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power (P) = voltage (V) x current (I)
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determines how much electrical energy a device uses
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power (voltage x current) and the length of time the device is on
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unit for measuring electricity per unit time
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kilowatt-hour
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materials through which current flows easily
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conductors
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materials through which current does not easily flow
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insulators
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materials that are not good conductors or insulators
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semiconductors
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the amount by which an object hinders electron flow
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resistance
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unit of resistance
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ohm
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instrument used to measure resistance
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ohmmeter
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the heat that results from overcoming resistance
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Joule heat
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alloy of nickel, chromium, and iron that has a higher resistance than most metals
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nichrome
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the most important factor affecting the ease of current flow
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the type of material
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other factors that affect resistance
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the diameter of the conductor, the length of the conductor, temperature
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a material that allows current to flow with no resistance
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superconductor
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advantages of superconductors
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a tiny one can conduct a lot of current, there is no Joule heat, they can be used to make unusually powerful electromagnets
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the difficulty in using superconductors more
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a specific, extremely cold temperature is required for a material to become a superconductor
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the temperature at which a material becomes a superconductor
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critical temperature
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Ohm's law
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voltage (V) = current (I) x resistance (R)
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an electrical device designed to add resistance to a circuit
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resistor
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resistors whose level is easily changed
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variable resistors (rheostats)
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the path an electric current follows
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electric circuit
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three parts of an electric circuit
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source of current, set of conductors, load
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the source of current in a circuit
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battery, generator, or other power source
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device that transforms the electric energy into some other useful form of energy
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load
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a circuit that has a complete circle from source, through the load, and back to the source
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closed circuit
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a circuit with a gap
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open circuit
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a device that opens and closes a circuit
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switch
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occurs when current takes a shortcut through a circuit, never going through the load
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short circuit
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why a short circuit is dangerous
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it increases the current, producing a lot of Joule heat
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a narrow strip of metal with a higher resistance than the rest of a circuit
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fuse
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purpose of a fuse
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if a short circuit is created, the fuse overheats and breaks, opening the circuit before a fire can be caused
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an automatic switch that opens a circuit if there is too much current
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circuit breaker
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occurs when too many devices are connected to a single circuit
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overloaded circuit
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connected directly to the earth
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grounded
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a circuit with multiple loads that the current flows through one after the other
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series circuit
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how to measure resistance in a series circuit
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add the resistance of all the loads
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how to measure voltage in a series circuit
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add the voltages of each load (it is divided among them)
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circuit with multiple loads arranged so that they are in separate branches
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parallel circuit
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advantage of a parallel circuit
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if one load goes out, the others still work
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how to measure resistance in a parallel circuit
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the inverse of resistance equals the sums of the inverses of the resistance in each load
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how to measure voltage in a parallel circuit
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use Ohm's law for the whole circuit or for each part (it's the same in all branches)
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the first electric light suitable for household use
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incandescent lamp
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inventor of the incandescent lamp
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Thomas Edison
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thing wire in an incandescent lamp that is heated until it glows
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filament
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the white frosting inside a bulb
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silica
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the gas in a light bulb that makes it last longer
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halogens (bromine or iodine)
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more effective bulbs that produce light by passing a spark through a confined gas
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electric discharge lamps
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common electric discharge lamp
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fluorescent lamp
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coating on inside of a fluorescent bulb
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phosphor
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new design for fluorescent bulb allowing them more uses
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compact fluorescent lamps (CFLs)
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an electric discharge lamp filled with neon instead of mercury
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neon lamp
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color of a neon lamp
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crimson
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semiconductor devices that emit light when a direct current is applied
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light-emitting diodes (LEDs)
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why electricity and magnetism are fundamentally related
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they both stem from electromagnetic force
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a device that converts electricity to motion
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solenoid
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device invented to communicate over long distances using electromagnets
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telegraph
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the switch in a telegraph
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key
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code for talking on the telegraph
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Morse code
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an electrical switch operated by an electromagnet
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relay
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a device that converts pulses of electricity into sound waves
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loudspeaker
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parts of the telephone
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loudspeaker, microphone
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device that converts sound waves to pulses of electricity
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microphone
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most important device for converting electricity into motion
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electric motor
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scientist and theory from which the idea of the electric motor came |
Pierre le Pelerin, theory of perpetual motion |
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basic parts of electric motor |
armature, field magnet, commutator |
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part of the motor that reverses the current in the armature |
commutator |
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part of the motor that contains an electromagnet that can freely rotate |
armature |
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part of the motor that contains a stationary, permanent magnet |
field magnet |
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the cause of the rotation of the armature in a motor |
changing the direction of the current each half-turn |
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the kind of electricity produced by a simple motor |
DC |
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motor that does not have a commutator |
AC motor |
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what replaces the commutator in an AC motor |
slip rings |
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six sources of electricity |
light, friction, chemical reaction, motion in a magnetic field, pressure, heat |
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electricity produced by pressure |
piezoelectricity |
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electricity produced by heat |
thermoelectricity |
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electricity produced by rubbing |
static electricity |
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two ways light produces electricity |
photoelectric effect, photovoltaic effect |
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any device that uses a chemical reaction to produce electricity |
electrochemical cell |
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electrochemical cells which can be recharged |
storage cells |
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electrochemical cells which cannot be recharged |
voltaic cells |
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conductors which move electricity from an electrochemical cell to a load |
terminals |
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negative terminal |
anode |
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positive terminal |
cathode |
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what happens when several cells are joined in a series |
voltage is boosted |
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a group of cells grouped as a single source of electricity |
battery |
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what happens when cells are connected in a parallel arrangement |
current increases |
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showed that electric current can produce mechanical motion |
Hans Christian Oersted |
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showed that mechanical motion can produce electric current (using a magnetic force) |
Michael Faraday |
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the process of converting mechanical motion to electric current |
electromagnetic induction |
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a device that measures small electric currents |
galvanometer |
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ways to increase the strength of an electric current produced electromagnetically |
move the magnet more quickly, increase the strength of the magnet, increase the number of turns of wire in the coil |
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a device that uses electromagnetic induction to produce electricity |
generator |
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basic parts of an AC generator |
armature, field magnet, slip rings |
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small AC generators that recharge the battery of an automobile |
alternator |
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what a DC generator has instead of slip rings |
commutator |
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a generator that produces electricity in a fluid |
magnetohydrodynamic generator (MHD generator) |
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a device that spins at high speed when high-pressure steam passes through it |
steam turbine |
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purpose of a turbine |
to provide motion that can be converted to electricity |
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turbine that moves because of hot gases generated by burning fuel |
gas turbine |
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power plant that uses moving water to produce electricity |
hydroelectric power plant |
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ideas for new energy sources for producing electricity |
wind, sun, nuclear fusion |
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a device that increases or decreases the voltage of AC with electromagnets |
transformer |
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transformer that increases voltage |
step-up transformer |
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transformer that decreases voltage |
step-down tranformer |