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39 Cards in this Set
- Front
- Back
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what is an atom made up of? |
electrons, protons and neutrons |
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what is static electricity? |
when electrons rub off something and onto another object. the object that gains electrons are negatively charge and has a build up of static charge (electrons are stationary) |
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what are 3 things circuits require? |
-power source -load -conducting pathway |
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What is DC? |
Is direct current. Is when current moves in one direction through a current |
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what is AC? |
Alternate current. Keeps changing direction in the current |
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what is current? |
is the amount of charge (q) passing a point in a certain time |
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what is voltage? |
is the electrical potential energy. it "pushes" the electrons around the circuit |
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what is a wet cell? |
has 2 electrodes placed in liquid. they are heavy and the acid can easily spill. they can be recharged by forcing electrons to pass backwards trough the circuit. |
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what is a dry cell? |
are compact because they have one electrode wrapped around another. they don't leak because they use a conducting paste instead of a liquid |
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what is a photovoltaic cell? |
convert solar energy directly into electrical energy. |
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what is resistance? |
is how difficult (high pressure) or easy (low residence) it is for an electron to flow through a substance |
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what does resistance depend on? |
-the type of material -the length of the wire -diameter of wire |
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what are conductors? |
have low resistance and therefor electrons flow easily through them. |
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what are insulators? |
are poor conductors of electricity. they have very HIGH resistance |
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what are series circuits? |
are when all components are on a single line. (side by side) |
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what are the advantages and disadvantages of series circuits? |
advantages -all components get full current -can be used to lower voltage disadvantages -if one component break all of them stop working |
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what are parallel circuits? |
when multiple circuits are joined together |
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what are some advantages of parallel circuits? |
-one component breaks the others keep working -each circuit receives the same voltage -current can be manipulated |
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what are complex circuits? |
are circuits with both series and parallel circuits |
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what is household wiring? |
all wiring in a house is wired in parallel circuits. this means that all components receive maximum energy. and the component breaks the others keep working |
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what is the active wire? |
is brown and brings the current into the the appliance |
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what is the neutral wire? |
is blue and takes the current out of the house |
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what is the earth wire? |
is green and yellow and is the safety device wire. activates the fuse |
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what are some safety features of plugs? |
are insulators on the lead, external plug, plug and the active and neutral pins. |
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what are safety devices? |
are wired into the active line. this stops any current going into the appliance. |
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what are fuses? |
are high resistance and low melting point wire. if a short circuit occurs the current increases and melts the fuse. therefore breaking the circuit. |
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what is a circuit breaker? |
acts like a fuse but are only faster and much easier to reset. |
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what is a residual current device (RCD)? |
works by reading the current in against the current out from a house. if there are any difference between the two currents it switches off power in 0.03 seconds. |
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how do photovoltaic cells work? |
the energy in the sunlight knocks electrons off semiconducting silicon crystals within the cell. these electrons move away from the crystals forming an electrical current that can be used to power appliances. |
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what is magnetism |
magnets are surrounded by magnetic fields. these fields can attract -iron, nickel, cobalt and other magnets |
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what is the law of attraction |
- like poles repels - unlike poles attract |
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what is an electro magnet |
when an wire is wrapped around an iron bar it becomes an electro magnet |
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what are some advantages of electromagnets |
-can be turned on or off -1000 times stronger than ordinary magnets - strength of magnet can be changed by changing the current -poles can be reversed by reversing the current |
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what do electric motors do |
it uses a circuit with a power source to create movement |
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what do generators do? |
uses movement to create and electric circuit |
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what are turbines? |
are simply large generators. they need to be spun fast by water, wind and steam |
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how does water create electricity |
moving water pushes against the blades of a turbine, making them spin, which turns a large generator hence making electricity |
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describe steam power |
is produced by boiling water by burning coal which creates steam. the pressure of this steam turn the turbine to spin again making electricity |
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what is a transformer |
is a device that can increase or decrease AC voltage for transport and usage purposes |
