Electricity Flashcards
Law of electric charges (3 things)
Like charges repel
Unlike charges attract
Some neutral objects may be attracted to each other
What is the electrostatic series?
List of meterials that have been arranged according to their ability to hold on to electrons. Lower materials have stronger attraction. The further apart, the stronger the charge.
What is charge displacement?
When electrons can be forced to go to one side of an object, but since they dont leave it, the object remains neutral.
Insulator:
A material that doesn’t allow electrons to move freely between atoms. (electrons are tied up in chemical bonds)
Conductor
A material that does allow electrons to move freely between atoms. Most metal.s
What is grounding?
To connect an object through a conductor to the earth. The earth is neutral and because it is so big, it acts as a limitless source of electrons
How do dryer sheets work?
Hot air from the dryer vaporizes a waxy compound in dryer sheets. This coats the clothes and they behave like they are all the same material. Prevents static charges.
What is an electroscope, and how does it work?
An electroscope is a device used to detect charge. The charge is spread all over the electroscope and the leaves repel eachother. The result is the same whether it’s negative or positive.
What are the three ways to charge an object?
Friction, contact, induction.
Explain charging by friction.
2 different neutral materials are rubbed together. End up with opposite charge.
Explain charging by contact
A neutral object is touched by a charged object. Electrons are transformed from a negative to neutral/neutral to positive object. They will end up with the same type of charge. Charging object loses some charge.
Explain charging by induction.
A charged object is held close to a neutral object without touching. The neutral object is grounded. The neutral object will attract electrons from the ground if the charge is positive, and lose electrons to the ground if the charge is negative. The charging object is then removed, and the object end up with opposite charges.
Cell:
A device that converts chemical energy to electrical energy.
Who made the first battery, and what was it like?
Allessandro Volta. Created a “voltaic pile” which was the first battery. It was made out of alternating disks of silver and zinc, separated by a piece of cloth soaked in salt water.
What is a battery?
A connection of two or more cells.
Electrode:
One of two metal terminals in a cell or battery
Electrolyte:
A solution or paste that can conduct charge
Primary vs secondary cells:
Primary can be used once, secondary can be recharged.
What is current electricity?
The flow of electrons through the conductor.
What is required for electrons to flow?
A closed circuit.
What 3 essential components are in a circuit?
Cell
Load
Conductor wires
Load:
A device that transforms electrical energy to other kinds of energy.
What is a terminal?
A metal component on a cell that supplies electrons (-) or recieves electrons (+)
What is a switch?
A device that opens or closes a circuit.
What is an electric current?
A measure of the number of electrons that pass a certain point in a circuit in a certain time.
Current is only measured with an ammeter connected in ___
series
What is the equation for current?
I=q/t
Energy:
The ability to do work
Define potential difference
The energy per coulomb
Explain potential difference
Electrons pick up energy at the power source and give some up at each load. A circuit works so that the total energy picked up at power source equals energy lost in the trip. The energy gained or lost by each coulomb of electrons in the potential difference.
What is the equation for potential difference?
V=E/q
How are cells connected in series vs parallel?
Dry cells are connected in series when they are connected end to end. Positive terminals are connected to negative terminals.
Dry cells are connected in parallel when they are connected side by side. Positive is connected to positive and negative to negative. Energy is picked up only once because each electron only goes through one cell.
What is power?
The rate at which energy can be transferred or transformed.
What is the equation for power?
P=E/t
Define resistance
The ratio of the potential difference across a load to the current through it.
A resistor is a ____ element.
heating
How are resistors useful?
They control the current in a circuit through different branches. More electrons take the path of resistance.
What is the equation for resistance?
R=V/I
What does resistance depend on? (4)
Length (longer has more resistance), material, diameter (thicker has less resistance), temperature (resistance may decrease or increase as heats up)
Series: xt=x1=x2=x3
I (current is the same all around bc electrons have nowhere else to go.
Parallel: xt=x1=x2=x3
V (potential difference is lost in only one branch)
Resistance calculated in parallel series diagram?
1/RT=1/R1….
What happens if a light goes out in series vs parallel?
In series they all go out because there is one path, but in parallel only one goes out and the rest stay on because they aren’t in the same path.
What is a circuit breaker, and how does it work?
A switch that opens when a specific current is exceeded. Head causes a bimetallic stript o bend, which creates a break in the circuit. When it cools down it can be reset. Brass in the strip expands more than iron while heated so it bends.
Cost of electricity equation
Total cost=E x rate
=pt x rate
What does efficiency measure?
How much energy is coming out of an appliance.
What is the efficiency equation?
Eout/Ein x 100%
What is Ein/Eout?
Ein: Energy the appliance uses
Eout: Desired energy the appliance omits.
What is Faraday’s law?
A moving (or otherwise changing) magnetic field can cause an electric current to flow in a conductor.
What is a transformer?
A device that increases or decreases the potential difference in a system.
How is electricity distributed?
Electricity is reduced when electricity is transmitted at a high potential difference or a low current.
What are the top 3 energy sources in canada?
Hydro, Nuclear, Coal
How does a hydroelectric plant work?
Water from reservoir flows into dam, travels through penstock, moving water spins turbines which power a generator.
Advantages/disadvantages of hydro
Advantages: 90% efficient because almost no heat transformations, no fuel costs, no combustion emissions
Disadvantages: Flood land, submerged vegetation decays releasing methane and mercury.
How does a nuclear plant work?
Heat energy released during the fission of uranium become electrical energy by usingheavy water to transfer energy from the reactor to the water, generating steam which turns turbines which powers the generator.
Advantages/disadvantages of nuclear
Advantages: large amounts of energy for small amounts of fuel, no greenhouse gasses, inexpensive once power stations are build
Disadvantages: Power stations are expensive, uranium is non-renewable, mining, warmed coolant water can damage aqueous ecosystems.
How does a coal plant work?
Heat created by burning coal boils water, creates steam which turns blades of turbines which are connected to generators.
Advantages/disadvantages of coal
Advantages: Large known reservoirs of coal, costs are low
Disadvantages: The conversion of energy from coal to electric is inefficient, burning coal produces emissions i.e. CO2, acid rain/particulates, non-renewable
Base load:
The continuous minimum demand for electrical power.
Intermediate load:
A demand for electricity that is greater than base load ( and it met by burning coal and natural gas. )
Peak load
The greatest demand for electricity (met by using hydro and natural gas)
Renewable energy vs non-renewable enrgy
Renewable can be replaced in a relatively short period of time. Non-renewable cannot be replaced as quickly as it is used.
Fuse:
Device that melts when maximum current is exceeded. Used only once.
Turbine:
Device that is turned by water or steam to operate an electrical generator.
Fission:
Reaction in which an atomic nucleus splits, releasing energy.
Generator:
Device that converts mechanical energy to electrical energy.
