Electricity Chapter 12

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  1. Direct current (DC)
    • Current in which charged particles travel through a circuit in only one direction.
    • In a circuit containing a cell the electrons travel from the negative terminal to the positive terminal in only one direction.
  2. Alternating current (AC)
    • Current in which electrons move back and forth in a circuit.
    • Since they move back and forth, there is no net movement of electrons.
    • Alternating current is used in our electrical grid since AC can be used with transformers which allows us to transmit electricity at high potential differences and low currents which loses less energy.
  3. Transformer
    • An electrical device that changes the size of the potential difference of an alternating current.
    • There are two kinds of transformers; step-up transformers that increase the potential difference, these are used to increase the potential difference after electricity is generated, and step-down transformers, that decrease the potential difference so that appliances in our homes can use the electricity.
    • The electricity you use at home has most likely gone though around five transformers before it got to you to use.
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  4. Circuit breaker
    • A safety device that is placed in series with other circuits, which lead to appliances and outlets.
    • When the current is too large, a part of the circuit breaker is heated and bends; this breaks contact with another part and then opens the circuit. The circuit breaker must then be reset after this.
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  5. Fuse
    • A safety device found in older buildings and some appliances; like a circuit breaker, it is places in series with other circuits, which lead to appliances and outlets.
    • A fuse contains a metal conductor that melts at a temperatures corresponding to a set amount of current, which creates an open circuit and stops the current; it must be replaced after this happens.
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  6. Electrical power
    • The rate at which an appliance uses electrical energy.
    • Some appliances use electricity more efficiently and have lower electrical power consumption yet still have the same useful energy output, such as a fluorescent bulb compared to an incandescent bulb. Some appliances just have to use more electricity such as an electric stove compared to an incandescent light bulb.
  7. Watt (W)
    • A unit of electrical power.
    • 1 Watt is equal to 1 Joule per second.
  8. Kilowatt (kW)
    A practical unit of electrical power; 1kW = 1000W
  9. Electrical energy
    The energy that is used by an appliance at a given setting; determined by multiplying the power rating of an appliance by the length of time it is used
  10. Kilowatt-hour (kW*h)
    • The practical unit of electrical energy.
    • The joule is the unit for any form of energy and could be used instead, however joules are too small to be practical and it is easier to think in of electrical usage in hours rather than seconds (since a joule is equal to a W*s).
  11. EnerGuide label
    • A label that gives detail about how much energy an appliance uses in one year of normal use.
    • Information present on the label includes: the average yearly power consumption in kW*h, a line to compare energy consumption to other similar appliances, and an energy star certification if it uses 10% to 50% less energy then an average comparable appliance.
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  12. Smart meter
    • A meter that records the total electrical energy used hour by hour and sends this information to the utility company automatically.
    • Smart meters are necessary for the new time of use electricity pricing in Ontario.
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  13. Time of use pricing
    A system of pricing in which the cost of each kW*h of energy used is different at different times of the day. There are off-peak, mid-peak, and on peak-pricing; each more expensive than the last. These prices are adjusted twice a year for summer and winter electricity use. It is also always off-peak pricing on the Weekends and on any holiday. This pricing method encourages people to use electricity at off-peak hours when it is cheaper to generate electricity.
  14. Phantom load
    • The electricity that is consumed by an appliance or device when it is turned off.
    • Some examples include: clock displays on microwaves, the ability for a TV to sense an IR signal from a remote when it’s off, and external power adapters. It is estimated that the average home has a phantom load of about 50W.
  15. Efficiency
    • The ratio of useful energy output to total energy input, expressed as a percentage.
    • Percent efficiency= (useful energy output (Pout) / total energy input (Pin))*100%
    • The total energy input is its power multiplied by the time it is on. Since a joule is one watt operating for one second (1J = 1W*s). Often kW and kJ are used since J and W themselves are too small for practical purposes.
  16. Base load
    • The continuous minimum demand for electrical power.
    • In Ontario the base load is about 12GW (1GW = 109 W). The base load in Ontario is mainly generated by nuclear generators, hydroelectric generators, and some coal-fired generators.
    • Off-peak hours are during base load.
  17. Hydroelectric power generation
    • The generation of electrical power using a source of moving water.
    • There are two types; dam stations and run-of-river stations. In dam stations water falls between different levels in a dam to turn turbines, and in run-of-river stations the water of a flowing river is used. The generating stations at Niagara Falls are examples of run-of-river stations.
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  18. Intermediate load
    • A demand for electricity that is greater than the base load and is met by burning coal and natural gas.
    • Intermediate load is approximately 15GW to 20GW and is met by generating stations that burn fossil fuels. This increase in generating stations increases the cost and this represents the mid-peak rates.
  19. Peak load
    • The greatest demand for electricity, which is met by using hydroelectric power and natural gas.
    • In Ontario peak load above 20GW; this represents the highest cost for electricity or on-peak rates.
  20. Renewable energy source
    • A source of energy that can be replaced in a relatively short period of time.
    • Some examples include: hydroelectric generation, photovoltaic cells, tidal generation, ocean wave generation, geothermal, etc.
  21. Non-renewable energy source
    • A source of energy that cannot be replaced as quickly as it used.
    • All methods of generating electricity that involve burning fossil fuels are non-renewable as well as nuclear power since fossil fuels and uranium are both limited resources.
  22. Solar energy
    • Energy that is directly converted from the Sun into electricity.
    • Photovoltaic solar panels are a method of generating electricity through solar energy.
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  23. Photovoltaic effect
    • The generation of a direct current when certain materials are exposed to light.
    • In traditional photovoltaic panels, photons of light hit the electrons in silicon and knock them out of place. They then travel to thin wires that cross on top the silicon and generate a direct current.
  24. Biomass energy
    • Energy that is generated from plant and animal matter.
    • The process is said to be “carbon neutral” since burning plants only releases the same amount of carbon as they absorbed during their growth. However, some plants get buried and turn into fossil fuels in a natural cycle so the process of burning biomass does, at least in the long run, release more carbon than a natural cycle.
    • Biomass burning does not create much acid rain and does not release heavy metals into the atmosphere.
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Electricity Chapter 12
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