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Science 9 > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is the theory of electric charge?

A

A theory that proposes that electrons moving can create electricity and be used to perform a wide variety of tasks

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2
Q

What is a shortage/excess of electrons called?

A

Static electricity/unbalanced charges

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3
Q

Who first described charges as positive or negative?

A

Benjamin Franklin

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4
Q

What does the Law of Charges state?

A
  1. Like charges repel
  2. Unlike charges attract
  3. Charged objects attract neutral ones
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5
Q

What makes up an atom?

A

Positive protons and neutral neutrons in the center and negative electrons orbiting it

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6
Q

What parts of atoms can move?

A

Electrons

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7
Q

What are insulators and conductors?

A

Conductors allow electrons to flow freely through it while Insulators do not

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8
Q

What are semiconductors?

A

Materials with a higher conductivity than insulators but lower than conductors that can often have their conductivity increased

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9
Q

What are superconductors?

A

Materials that offer 0 resistance to electron flow

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10
Q

What is electric discharge?

A

When static electricity on an object balances with another by having electrons jump from one surface to another in a process called neutralization

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11
Q

How would someone discharge electricity safely?

A

Ground a wire

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12
Q

How would someone prevent electrostatic buildup?

A

Antistatic sprays can scatter the charge

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13
Q

What is an electric circuit?

A

An environment in which electrons can flow through a closed path freely

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14
Q

What are the 4 parts of a circuit?

A

Load (bulb), Source (cell), Switch (knife switch) and conductor (wire)

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15
Q

What is a battery?

A

A combination of cells

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16
Q

What is a resistor?

A

Anything that can slow down the flow of electrons by transferring electrical energy into usually heat

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17
Q

How would someone measure electrical current?

A

Ammeter for the largest, milliammeter for less, and galvanometer for miniscule amounts

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18
Q

What unit is current in?

A

Amperes (A), named after André-Marie Ampère

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19
Q

What is electric current?

A

How fast electrons are moving in a circuit

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20
Q

What is voltage?

A

The difference in electric potential/energy between 2 points, or how much energy it takes to push something across the two points (also known as potential difference)

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21
Q

What unit is voltage in?

A

Volts (V), named after Alessandro Volta

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22
Q

What is the symbol for current?

A

I

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23
Q

What is the symbol for voltage?

A

V

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24
Q

How is voltage measured?

A

Voltmeter

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25
Q

How is a water wheel similar to an electric circuit?

A

Reservoir=cell=source, Water wheel=bulb=load, Pipes=wires=conductor, Valve=switch=switch

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26
Q

What unit is resistance in?

A

Ohms(Ω), named after Georg Ohm

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27
Q

What is the symbol for resistance?

A

R

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28
Q

How is resistance measured?

A

Ohmmeter

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29
Q

What is Ohm’s law?

A

V=IR

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30
Q

What are rheostats?

A

Variable resistors

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31
Q

What are series circuits?

A

A circuit made up of one circuit/path for electrons to flow

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32
Q

What are parallel circuits?

A

A circuit made up of more than one path for electrons to flow, each separate loop acting like a single series circuit (each part of a parallel circuit is called a branch)

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33
Q

How is household electricity wired?

A

In parallel

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34
Q

How is a voltmeter wired?

A

In parallel

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35
Q

How is an ammeter wired?

A

In series

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36
Q

What determines the resistance of a wire?

A

Image 12

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37
Q

What does a multimeter do?

A

Combines Ohmmeter, voltmeter and ammeter all into one

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38
Q

What does a fuse do?

A

Burn up and disconnect the circuit in case it is too strong as a safety measure

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39
Q

How is a circuit supposed to be drawn?

A

RECTANGLE

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40
Q

How do thermocouples work?

A

When one end is heated, and the other cooled, it creates a very small electric current

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41
Q

What is a thermopile?

A

Several thermocouples connected in series

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42
Q

What is a thermo-electric generator?

A

A generator that uses a cooling fan and heat to make the thermopile output an electric current

43
Q

What is the piezoelectric effect?

A

When a solid such as quartz experiences a potential difference, it begins to vibrate

44
Q

Who discovered the piezoelectric effect?

A

Pierre and Jacques Curie (Pierre was Marie Curie’s husband)

45
Q

How do barbeque lighters work?

A

When a piezoelectric crystal is pushed, and electric current is generated that burns the butane and lights the fire

46
Q

How do LEDs work?

A

Light emitting diodes work by having components that glow when electricity is run through, is run by a semiconductor, and only work when connected in a specific direction

47
Q

What is a Photovoltaic cell?

A

It is a device made of a semiconductor that emits electrons when light hits it

48
Q

How was the electrochemical cell invented?

A

When Luigi Galvani found that a frog’s leg would twitch when 2 different metals were brought to it, he theorized that the animals themselves had electricity flowing through them. However, Alessandro Volta thought the electricity was coming from the metal. The debate ended with Volta’s discovery of oxidation, or where one material releases electrons when in contact with a salt/acid solution while the other absorbs it. This made the first cell, and if you stacked them on top of each other in series, it created the voltaic pile (see image 13)

49
Q

What are the parts of an electrochemical cell?

A

2 electrodes (an anode and cathode for the negative and positive sides), an electrolyte (a substance in which electrons can flow well) and a wire connecting the electrodes

50
Q

What is the difference between a primary and secondary cell?

A

Primary cells soon lose electrons to oxidate while Secondary cells can be “recharged” by forcing electrons through the opposite direction and allowing oxidation to happen again

51
Q

What are some common types of cells?

A

see image 14

52
Q

What is an electric generator?

A

Anything that converts motion into electricity

53
Q

Who discovered that electricity and magnetism had a relationship?

A

Hans Christian Oersted when he put a circuit next to a compass and saw the needle move with it

54
Q

What is an electromagnet and how does it work?

A

It is a wire wrapped around an iron core that becomes magnetic and creates a north and south pole when electricity is ran through it (see image 15)

55
Q

Who is Michael Faraday and what did he do?

A

He is credited with discovering the basic principles of electromagnetism and introduced the terms ion, cathode, anode, and electrode

56
Q

How do you induce voltage into a circuit using a magnet?

A

You move the magnet close to the wire and voltage is created

57
Q

How do you make an electromagnet stronger?

A

Use a better material, wrap it around the iron more times, increase current

58
Q

What liquids are strong electrolytes?

A

Salt and acid solutions

59
Q

What materials are good electrodes?

A

Copper, Zinc, Nickel, Aluminum etc. DO NOT USE 2 OF THE SAME ELECTRODE

60
Q

How does an AC generator work?

A

Tip: Think of it as how the north pole of a magnet attracts electrons. When the magnets spin, it starts to induce a current in the wire. When it reaches 90 degrees or perpendicular to the magnets, the voltage is at its highest. When it rotates 180 degrees after that, the north and south poles swap, causing the current to move in the other direction. This constant switching of the current allows electricity to be generated. (Because moving magnetic fields can push and pull electrons (see images 16, 17)

61
Q

Why do most power plants use AC generators?

A

It is easy to increase or decrease the voltage

62
Q

How do dynamos work?

A

Dynamos or DC generators are generators that output direct current and are basically AC generators with a split-ring commutator to reverse the current again to make it direct

63
Q

How do DC motors work?

A

Electricity spins the split-ring commutator and allows the brushes to transmit the current into the armature, which acts as an electromagnet that gets its poles constantly switched

64
Q

How do AC motors work?

A

With a stator(electromagnet) and rotor, the attraction and repulsion between the permanent magnets and the stator allows the motor to spin

65
Q

What are transformers?

A

Devices that can increase or decrease voltage to allow for easier transportation. They can be step-up transformers for easier transportation or step-down transformers for easier use

66
Q

What is the difference between a step-up and step-down transformer?

A

A transformer is always an iron square with wires wrapped around it and a step-up transformers has more coils on the output whereas a step-down has less coils on the output (see image 19)

67
Q

What do breaker panels do?

A

The circuit breakers inside act as a fuse for electricity flowing through your home but bend instead of burn

68
Q

What do fuse boxes do?

A

They are breaker panels but have a fuse instead of a circuit breaker that melts

69
Q

What do power meters do?

A

They are a part of the service panel that measures how much electricity is flowing into your home for utility bills

70
Q

What are branch circuits?

A

Circuits that connect electricity to all parts of your home, each with its own branch breaker in case of overheating

71
Q

What are the 3 parts of an electric cable?

A

Black/hot wire, White/Neutral wire, Copper/Green/Ground wire

72
Q

What is the electrical code?

A

A set of standards that need to be met by electricians after wiring a house

73
Q

How does digital electric technology work?

A

Millions of transistors act like switches and many circuits are programmed to do many different things

74
Q

What is power?

A

Energy per unit time

75
Q

What is electric power?

A

The amount of energy that is converted every unit of time

76
Q

What is the watt?

A

1 joule of energy per second or P=E/t

77
Q

How else can electric power be calculated?

A

P=IV

78
Q

What is a kWh?

A

A kilowatt hour is the energy used when a 1000W load is used for 1 h

79
Q

How do you read a power meter?

A

Each dial represents a number

80
Q

What do Energuide labels do?

A

They help people compare appliances by showing the average yearly kwh consumption that is regulated by the CSA(Canadian Standards Association)

81
Q

How do you calculate electric efficiency?

A

Useful energy output/Total energy input x 100%

82
Q

What are incandescent bulbs and how efficient are they?

A

They work by glowing a tungsten filament and only are 5 % efficient

83
Q

What are halogen bulbs and how efficient are they?

A

They are filled with a high-pressure gas, last 2-6 times longer than incandescent bulbs, and are 15% efficient

84
Q

What are fluorescent tubes and how efficient are they?

A

They are filled with a mercury vapor that emits light when an electrode emits electricity. They last 10-13 times longer than incandescent bulbs and are around 20% efficient

85
Q

Does current or voltage kill?

A

Current, although a high voltage is needed due to the high resistance of the human body (2mA can kill a human)

86
Q

How do you make electricity safe indoors?

A

Do not plug in too many electric devices to one outlet, do not touch appliances that are still plugged in, replace frayed cords, use receptable covers (white surrounding material) and never let appliances touch water

87
Q

What are short circuits?

A

A circuit without a load, causing the wire to heat up very fast and cause a fire

88
Q

How do you make electricity safe outdoors?

A

Don’t touch anything touching a wire, don’t dig where you aren’t supposed to, and don’t use appliances when it is raining

89
Q

How do thermoelectric generators work?

A

They burn a substance to make steam, then use the steam to spin a turbine

90
Q

What is the difference between a renewable and non-renewable resource?

A

One can be used infinitely while the other is being used faster than it is being replenished

91
Q

What is open-pit mining?

A

Mining out of a big open pit

92
Q

What are tailing ponds?

A

Ponds that have had waste materials from mines seep into the water, severely contaminating it

93
Q

What is the most common fuel for thermoelectric power plants?

A

Coal

94
Q

What do scrubbers do?

A

They spray a chemical solution into the exhaust pipe of a power plant and have the gases react with the chemicals to stop them from spreading out and creating acid rain

95
Q

What are greenhouse gases?

A

Any gas that helps trap heat within the earth

96
Q

How do hydroelectric plants work?

A

They get falling water to spin massive turbines that create electricity

97
Q

What are some of the downsides of hydroelectric dams?

A

They need to create a reservoir, which ends up flooding a lot of homes and destroying lots of habitats

98
Q

How does a nuclear plant work?

A

They bombard uranium with neutrons, causing nuclear fission and a tremendous amount of energy to be released. This energy in the form of heat is then carried off to spin a turbine

99
Q

What are the downsides of a nuclear plant?

A

Radioactive waste materials that cannot be safely handled

100
Q

What could the future of nuclear plants work?

A

By using a type of nuclear fusion instead of fission similar to the sun, we could create no such waste and even more energy

101
Q

What is thermal pollution?

A

The pollution of water systems by releasing hot waste water from the transportation of heat inside the plant, raising water temperatures and damaging the environment

102
Q

How does cogeneration work?

A

It uses the waste hot water to power residential or other industrial areas

103
Q

What are some alternative renewable energy sources?

A

Wind turbines (which don’t work on a windless day) Solar panels (which don’t work when there is no sunlight and are expensive), Reflective solar mirrors (to heat a liquid are useless when there is no sunlight) Tidal energy (which is only usable in a few places around the world) and geothermal energy (which only a few places around the world have the right conditions for it)

Science 9 (5 decks)

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