Chapter 12

Definition: current in which charged particles (electrons) flow through a circuit in only one direction

Extra Info: DC is found in batteries.

Example: Cell phone, flashlight. (use batteries)

Definition: current in which charged particles (electrons) move back and forth in a circuit

Extra Info: AC does not have a net direction of flow (it is zero) because the amount of electrons that go one way is equal to the amount moving in the opposite direction, so they cancel each other out and leave zero.

• Example: Refrigerator, dryer. (Plug into wall)
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Definition: an electrical device that changes the size of the potential difference of an alternating current

Extra Info: There are different types of transformers. Transformers that increase potential difference are called step-up transformers, while ones that decrease it are called step-down transformers.

• Example:
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Definition: a safety device that is in series with other circuits, which lead to appliances and outlets

Extra Info: Circuit breakers work by being heated by the current, and if the current is too high, a part of the circuit breaker will snap from the heat, causing an open circuit.

• Example:
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Definition: a safety device mostly found in old buildings, and does a job similar to the circuit breaker using a similar method

• Example:
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Definition: the rate at which an appliance uses electrical energy

Extra Info: The power rating of an appliance can be found on an EnerGuide label. It is used to find the energy used, and the cost of the energy.

Example: The power rating of a typical toaster is 1.1kW.

Definition: a unit of electrical power

Extra Info: 1,000 watts is equal to one kilowatt.

Definition: a practical unit of electrical power

Extra Info: Kilowatt is often used over watt because most devices use large amounts of electricity, easier measured in kilowatts. 1,000 watts is equal to one kilowatt.

Definition: the energy that is used by an appliance at a given setting; determined by multiplying the power rating of an appliance (P) by the length of time it is used (t)

Definition: the practical unit of electrical energy

Extra Info: Since most appliances are used for hours at a time, kW.s (kilowatt x seconds) is not as practical.

Definition: a label that gives details about how much energy an appliance uses in one year of average use

Extra Info: On EnerGuide labels, there is often a scale that shows how much energy the appliance uses compared to other appliances of the same type (the appliance that uses the least amount of energy would be better money wise).

• Example:
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Definition: a meter that records the total electrical energy used hour by hour and sends the information to the utility company automatically

Extra Info: Ontario's goal was to replace all old meters with smart meters in every house by the year 2010.

• Example:
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Definition: a system of pricing in which the cost of each kW.h of energy used is different at different times of the day

Example: The cost for energy would be higher in the morning when most people heat their houses.

Definition: the electricity that is consumed by appliances or devices when they are turned off

Extra Info: This can be prevented by unplugging the appliance/device and turning off any power rods.

Definition: the ratio of useful energy output to total energy input, expressed as a percentage

Extra Info: Percent efficiency can be found by dividing the useful energy output by the total energy input, then multiplying by 100.

• Example: (1kW= 1kJ)
• Percent efficiency=

• useful energy output
• total energy input        ^x100
• 168 kJ
• 198kJ    ^x100

0.84848484  x100

84.848484

• Therefore, the percent efficiency is approximately 85%.

Definition: the continuous minimum demand for electrical power

Extra Info: The electrical energy generating method optimally suited for meeting the base load is nuclear energy, and hydroelectric energy.

Definition: the generation of electrical power using a source of moving water

• Example: Dam station, run-of-river station (both are used to turn turbines).
• Dam station:
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• Run-of-river station (diagram):
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Definition: a demand for electricity that is greater than the base load and is met by burning coal and natural gas

Definition: the greatest demand for electricity, which is met by using hydroelectric power and natural gas

Definition: a source of energy that can be replaced in a relatively short period of time

Example: Hydroelectric energy, biomass energy (biofuels), wind energy, solar energy.

Definition: a source of energy that cannot be replaced as quickly as it is used

Example: Fossil fuel energy, nuclear energy, coal energy.

Definition: energy that is directly converted from the Sun into electricity

• Extra Info: This is done using solar panels, and the photovoltaic effect.
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• Solar panels are very expensive, but cost little to operate, but the cost of solar panels will decrease majorly in the coming decades.

Definition: the generation of a direct current when certain materials are exposed to light (e.g. the material of solar panels)

Definition: energy that is generated from plant and animal matter

Extra Info: This source of energy is renewable, and only releases as much carbon dioxide into the atmosphere as the plants absorbed during their growth ("carbon neutral"). A large supply of biomass is not always available for this however.