Electricity Flashcards
What is the theory of electric charge?
A theory that proposes that electrons moving can create electricity and be used to perform a wide variety of tasks
What is a shortage/excess of electrons called?
Static electricity/unbalanced charges
Who first described charges as positive or negative?
Benjamin Franklin
What does the Law of Charges state?
- Like charges repel
- Unlike charges attract
- Charged objects attract neutral ones
What makes up an atom?
Positive protons and neutral neutrons in the center and negative electrons orbiting it
What parts of atoms can move?
Electrons
What are insulators and conductors?
Conductors allow electrons to flow freely through it while Insulators do not
What are semiconductors?
Materials with a higher conductivity than insulators but lower than conductors that can often have their conductivity increased
What are superconductors?
Materials that offer 0 resistance to electron flow
What is electric discharge?
When static electricity on an object balances with another by having electrons jump from one surface to another in a process called neutralization
How would someone discharge electricity safely?
Ground a wire
How would someone prevent electrostatic buildup?
Antistatic sprays can scatter the charge
What is an electric circuit?
An environment in which electrons can flow through a closed path freely
What are the 4 parts of a circuit?
Load (bulb), Source (cell), Switch (knife switch) and conductor (wire)
What is a battery?
A combination of cells
What is a resistor?
Anything that can slow down the flow of electrons by transferring electrical energy into usually heat
How would someone measure electrical current?
Ammeter for the largest, milliammeter for less, and galvanometer for miniscule amounts
What unit is current in?
Amperes (A), named after André-Marie Ampère
What is electric current?
How fast electrons are moving in a circuit
What is voltage?
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)
What unit is voltage in?
Volts (V), named after Alessandro Volta
What is the symbol for current?
I
What is the symbol for voltage?
V
How is voltage measured?
Voltmeter
How is a water wheel similar to an electric circuit?
Reservoir=cell=source, Water wheel=bulb=load, Pipes=wires=conductor, Valve=switch=switch
What unit is resistance in?
Ohms(Ω), named after Georg Ohm
What is the symbol for resistance?
R
How is resistance measured?
Ohmmeter
What is Ohm’s law?
V=IR
What are rheostats?
Variable resistors
What are series circuits?
A circuit made up of one circuit/path for electrons to flow
What are parallel circuits?
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)
How is household electricity wired?
In parallel
How is a voltmeter wired?
In parallel
How is an ammeter wired?
In series
What determines the resistance of a wire?
Image 12
What does a multimeter do?
Combines Ohmmeter, voltmeter and ammeter all into one
What does a fuse do?
Burn up and disconnect the circuit in case it is too strong as a safety measure
How is a circuit supposed to be drawn?
RECTANGLE
How do thermocouples work?
When one end is heated, and the other cooled, it creates a very small electric current. Different than bimetallic strip
What is a thermopile?
Several thermocouples connected in series
What is a thermo-electric generator?
A generator that uses a cooling fan and heat to make the thermopile output an electric current
What is the piezoelectric effect?
When a solid such as quartz experiences a potential difference, it begins to vibrate
Who discovered the piezoelectric effect?
Pierre and Jacques Curie (Pierre was Marie Curie’s husband)
How do barbeque lighters work?
When a piezoelectric crystal is pushed, and electric current is generated that burns the butane and lights the fire
How do LEDs work?
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
What is a Photovoltaic cell?
It is a device made of a semiconductor that emits electrons when light hits it
How was the electrochemical cell invented?
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)
What are the parts of an electrochemical cell?
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
What is the difference between a primary and secondary cell?
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
What are some common types of cells?
see image 14
What is an electric generator?
Anything that converts motion into electricity
Who discovered that electricity and magnetism had a relationship?
Hans Christian Oersted when he put a circuit next to a compass and saw the needle move with it
What is an electromagnet and how does it work?
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)
Who is Michael Faraday and what did he do?
He is credited with discovering the basic principles of electromagnetism and introduced the terms ion, cathode, anode, and electrode
How do you induce voltage into a circuit using a magnet?
You move the magnet close to the wire and voltage is created
How do you make an electromagnet stronger?
Use a better material, wrap it around the iron more times, increase current, larger iron core
What liquids are strong electrolytes?
Salt and acid solutions
What materials are good electrodes?
Copper, Zinc, Nickel, Aluminum etc. DO NOT USE 2 OF THE SAME ELECTRODE
How does an AC generator work?
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)
Why do most power plants use AC generators?
It is easy to increase or decrease the voltage due to its changing magnetic field, and a changing magnetic field is required for conventional transformers to work
How do dynamos work?
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
How do DC motors work?
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
How do AC motors work?
It is made up of a stator, which is an iron tube filled with copper wires on the sides. When an electromagnet is added and connected to the copper wires, when the system is powered the electromagnet starts to spin
What are transformers?
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
What is the difference between a step-up and step-down transformer?
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)
What do breaker panels do?
The circuit breakers inside act as a fuse for electricity flowing through your home but bend instead of burn
What do fuse boxes do?
They are breaker panels but have a fuse instead of a circuit breaker that melts
What do power meters do?
They are a part of the service panel that measures how much electricity is flowing into your home for utility bills
What are branch circuits?
Circuits that connect electricity to all parts of your home, each with its own branch breaker in case of overheating
What are the 3 parts of an electric cable?
Black/hot wire, White/Neutral wire, Copper/Green/Ground wire
What is the electrical code?
A set of standards that need to be met by electricians after wiring a house
How does digital electric technology work?
Millions of transistors act like switches and many circuits are programmed to do many different things
What is power?
Energy per unit time
What is electric power?
The amount of energy that is converted every unit of time
What is the watt?
1 joule of energy per second or P=E/t
How else can electric power be calculated?
P=IV
What is a kWh?
A kilowatt hour is the energy used when a 1000W load is used for 1 h
How do you read a power meter?
Each dial represents a number
What do Energuide labels do?
They help people compare appliances by showing the average yearly kwh consumption that is regulated by the CSA(Canadian Standards Association)
How do you calculate electric efficiency?
Useful energy output/Total energy input x 100%
What are incandescent bulbs and how efficient are they?
They work by glowing a tungsten filament and only are 5 % efficient
What are halogen bulbs and how efficient are they?
They are filled with a high-pressure halogen gas accompanied by the incandescent base, last 2-6 times longer than incandescent bulbs, and are 15% efficient
What are fluorescent tubes and how efficient are they?
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
Does current or voltage kill?
Current, although a high voltage is needed due to the high resistance of the human body (2mA can kill a human)
How do you make electricity safe indoors?
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
What are short circuits?
A circuit without a load, causing the wire to heat up very fast and cause a fire
How do you make electricity safe outdoors?
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
How do thermoelectric generators work?
They burn a substance to make steam, then use the steam to spin a turbine
What is the difference between a renewable and non-renewable resource?
One can be used infinitely while the other is being used faster than it is being replenished
What is open-pit mining?
Mining out of a big open pit
What are tailing ponds?
Ponds that have had waste materials from mines seep into the water, severely contaminating it
What is the most common fuel for thermoelectric power plants?
Coal
What do scrubbers do?
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. They can also have sorbents
What are greenhouse gases?
Any gas that helps trap heat within the earth
How do hydroelectric plants work?
They get falling water to spin massive turbines that create electricity
What are some of the downsides of hydroelectric dams?
They need to create a reservoir, which ends up flooding a lot of homes and destroying lots of habitats
How does a nuclear plant work?
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
What are the downsides of a nuclear plant?
Radioactive waste materials that cannot be safely handled
What could the future of nuclear plants work?
By using a type of nuclear fusion instead of fission similar to the sun, we could create no such waste and even more energy
What is thermal pollution?
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
How does cogeneration work?
It uses the waste hot water to power residential or other industrial areas
What are some alternative renewable energy sources?
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)
