Download SNC4E Electricity Unit Electricity Introduction: Learning about

SNC4E
Electricity Unit
Electricity
Introduction: Learning about Electricity
Electricity is a form of energy. It is produced by all of the movement of electrons.
Electricity flows through electric circuits. Electrons travel through these paths, but only if
they can move around the path and get back to where they started. If the path is
broken, the electrons will not move.
A closed circuit allows electrons to travel through an unbroken path and back to where
they started.
An open circuit has a break in the path. Electrons will not move through an open
circuit.
All circuits must contain 3 things: connecting conductors, an energy source, and a load.
A conductor is a device, such as a wire, that allows electricity to pass easily through it.
An energy source, such as a battery, is what gives the circuit its energy. An energy
load is a device or appliance that uses the energy, such as a light bulb.
The flow of electrons around an electric circuit is measured by the current. Imagine that
each electron is a drop of water. The current would be like a river. In a river, there are
too many drops of water to count. In a similar way, there are too many electrons in a
current to count! To count them easily, we “package” electrons into groups of charger
called coulombs. Electric current is measured in amperes (A).
Potential energy is stored energy that can be used to do something. Electrons get their
energy from the potential energy stored in the energy source of a circuit.
A material that an electron flows through is called a conductor. Electrons move more
easily through some conductors than others. For example, copper is a better conductor
than iron. A material that is difficult for electrons to flow through is called a resistor.
Resistors restrict the flow of electrons. Resistance is a measure of how easily a current
can flow through a material. It is measured in ohms.
Now that you know that electrons need a circuit, or a path, to flow through. There are 2
kinds of circuits. 1. A series circuit is a circuit set up like a running track. There is only
one path for electrons to flow. 2. A parallel circuit is a circuit set up like a city series.
There are many paths for electrons to flow.
Information taken from: Agusta et al. ScienceWise (2003). Succeeding in Today’s World. Irwin Publishing
Indoor and Outdoor Safety
At Home
- Do not run extension cords under carpets. Extension cords are designed to be used
temporarily. If you need one permanently, you should install a new outlet closer to the
appliance.
- Never cut the ground pin off of a 3-pronged plug
- Never use tracks, staples, or nails to fasten extension cords permanently to walls or
baseboards.
- Do not plug too many appliances into one outlet. This can overload the circuit. Do not
use indoor extension cords outside.
Outdoors
- Never fly a kite or a model plane near overhead power lines.
- Never touch an electric wire that has fallen to the ground. Even if the wire does not
make a noise or a spark, it is still very dangerous.
- Never mix water and electricity. Electricity can travel through water. For example,
never mow the lawn with an electric mower when it is raining.
- Do not have electric cords near a pool.
In the workplace
- Use Canadian Standards Association (CSA) approved equipment.
- Follow all guidelines and rules provided.
- Practice proper lockout procedures on electric equipment. (Lockout is a safety
measure to protect against accidental operation when the operation of the equipment
and/or circuits could cause injury to a person.)
Information taken from: Agusta et al. ScienceWise (2003). Succeeding in Today’s World. Irwin Publishing
Practical Electricity
Now that we have a general idea of how electricity works, we will be looking at how we
use it. We will be looking at practical uses of electricity, problems and solutions of using
electricity, and how it relates to our daily lives.
Consumers and Electrical Devices
CD players, televisions, computers, lamps and clock radios are all electrical devices. On
the underside of many clock radios or small appliances are symbols from regulatory
agencies. But what do they mean to you, the consumer?
AC vs. DC Current
Some electrical devices are plugged directly into the AC outlet in your home. Others use
batteries or have adapters to convert AC current to DC current. Devices that require DC
current tend to be small, like flashlights and some radios. DC energy sources tend to
produce a low voltage. All large appliances, such as refrigerators, use AC because their
energy requirements are higher. The electricity supplied to our homes uses AC current.
But how do we know how much energy we use?
Measuring Electricity Use
Electric power is energy per unit time and is measured in watts (W) or kilowatts (kW).
Since electric power is energy used in a unit of time, multiplying power by the time
interval gives us the quantity of energy used.
For example, Hydro wants to know how much electricity is used over a certain time. We
pay for our electric energy use in kilowatt hours (kWh), that is, 1000 watts of energy
each hour.
Major Appliances and Energy Efficiency
If an appliance is efficient, it is using most of its power to do what you want it to do and
very little to do anything else. For example, an energy efficient light bulb produces light
and very little heat. This is exactly what you want it to do, because you want it to
produce the light but not the heat. Fluorescent light bulbs are more energy efficient than
incandescent light bulbs because they produce less heat.
Nothing is 100-percent energy efficient, but it is a good idea to figure out the energy
efficiency of an appliance before you but it. Did you know that a refrigerator accounts for
11 percent of the total energy consumed in your home? Major appliances sold in
Canada, such as refrigerators, washing machines and dishwashers, are required, by
law, to meet minimum energy efficiency standards. They are also required to have an
EnerGuide label, which helps to inform you before you buy.
Information taken from: Agusta et al. ScienceWise (2003). Succeeding in Today’s World. Irwin Publishing
EnerGuide
Includes a large number which tells you the energy in kilowatt hours the appliance uses
in a year. Less is better—the smaller the number the less energy it uses and the more
efficient the appliance is. Most major appliances have a lifespan of 10 to 15 years. So, if
you make a bad choice, you are stuck with it for a long while. As well, if the appliance
you chose is not energy efficient, you are stuck with the cost.
Society and Electricity
During the 1960s and early 1970s, many homes were wired using aluminum wiring
because it was cheaper than copper wiring. Aluminum is not as good a conductor as
copper. To make up for this, a wider gauge of aluminum needs to be used. It is
generally 1 size larger than the copper that would have been used.
Aluminum has other disadvantages:
- a greater expansion/contraction rat—increases the chance of connections loosening
- less elastic than copper—more likely to be damaged
- corrosion increases resistance and generates a lot of heat
When it was found that aluminum could cause electric fires, the use of aluminum wiring
in homes was eventually stopped. Many of the problems were found in the service
panels where the aluminum wire connected to another metal, not in the actual wiring of
the house. Many homes only need the connection redone. Anyone with aluminum wiring
in their home should seek expert advice.
Information taken from: Agusta et al. ScienceWise (2003). Succeeding in Today’s World. Irwin Publishing
Environmental Impact
How does the use of electrical devices affect the environment? The effects come from 2
sides. On the consumption side, producing the electricity necessary to run electrical
devices can have harmful effects on the environment. On the disposal side, getting rid
of electrical devices when we are done using them can also cause problems.
The Consumption Side
Each method of using energy has environmental impacts:
Coal-burning Power Plants We usually relate greenhouse gases, such as carbon
dioxide, to driving cars. However, coal-burning power plants, which produce a lot of the
electricity in some communities, also produce a large amount of the greenhouse gases.
Earth absorbs ultraviolet radiation from the sun during the day, and then reflects infrared
radiation into space. Greenhouse Gases gases that absorb infrared radiation,
heating up the atmosphere.
The sulphur found in coal is also released into the atmosphere when coal is burned.
This produces sulphur dioxide, a highly poisonous gas. When the sulphur dioxide mixes
with moisture in the air, it forms acid precipitation. Acid precipitation is rain, snow, or
hail that is much more acidic than it is supposed to be. It can cause severe damage to
forests, crops and buildings.
Nuclear Plants Nuclear power plants produce very large amounts of energy with very
little fuel. They do not produce greenhouse gases. However, they do produce nuclear
waste. Nuclear waste is made up of the products of the nuclear reactions. They are
highly radioactive and remain so for thousands of years. Radioactive substances break
down slowly and produce radioactive radiation. Radioactive radiation is made up of
particles and energy that can damage living cells. If an organism is exposed to large
amounts of radioactive radiation, it can die. As a result, release of these chemicals into
the environment can make large areas unlivable for any organism.
Dams The dams built for hydroelectric plants are quite large, Hydroelectricity used to
be considered an extremely clean and non-harmful way to produce electricity. But the
large dams flood the land behind them and can destroy entire ecosystems.
The dams also lower the water level in the front of them, drastically changing the
landscape. Aquatic animals that need a certain level of water to live are forced to leave
(or die), and land animals (including people) lose their homes. Altering the flow of the
river can alos destroy the river itself and ruin the drainage of its water system. The
result is like a clogged toilet: the river is inactive and the water does not flow.
Information taken from: Agusta et al. ScienceWise (2003). Succeeding in Today’s World. Irwin Publishing
The more electrical devices that we use, the more it is necessary to burn coal at our
coal-burning power plants, produce nuclear waste through our nuclear power plants and
use dams for hydroelectric plants.
The Disposal Side
The heavy metals (cooper, iron, etc.) found in electronic equipment, including
computers, stereos and appliances, are harmful to animals and plants. Heavy metals
can affect the way organisms live. For this reason, we must use caution when disposing
of our electrical devices. In fact, the best solution is to recycle the materials so that they
never need to go to the garbage.
Large Appliances Auto companies have been recycling the metals in old cars for
years. The same can be done with large appliances such as refrigerators, stoves,
washers, dryers and dishwashers. If the appliance is in good shape, it can be sold to a
retailer who is willing to fix it up and resell it. Otherwise, there are companies willing to
remove the harmful substances from them and recycle them.
Computers There are several companies that recycle computers. Most people replace
their computers long before they are ready for the garbage. There are many charitable
organizations that would appreciate the donation of a used computer. Other
organizations are happy to reuse and recycle the parts. The key is to not just throw it
into the garbage. The heavy metals that make up the outer case and internal parts are
dangerous to our health if they are thrown away.
Batteries Batteries contain toxic chemicals such as nickel and cadmium. Nickel and
cadmium are known carcinogens. Carcinogens are chemicals that can cause cancer.
Though most municipalities have rules about how to dispose of large appliances, none
have regulations about the disposal of the batteries used in flashlights, portable radios,
channel changers, etc. Proper disposal of batteries involves separating them from the
regular garbage so that they are never put in garbage dumps.
The Economy and the Environment
Our society depends on electricity and electrical devices. It would be unrealistic to ask
everyone to stop using electricity to save the environment. For many people, electricity
is necessary to make a living. It is part of the reason for our high standard of living. That
standard of living is also paid for by a healthy economy.
The economy and the environment are impossible to separate. Many feel that too much
attention to the pollution in the environment could hurt the economy. Recycling
programs can be expensive and may be paid for through an increase in taxes. That
leaves less money to spend on other things. However, others feel that too much
pollution hurts the economy. If there is a smog alert in the city, many people who might
Information taken from: Agusta et al. ScienceWise (2003). Succeeding in Today’s World. Irwin Publishing
have gone out shopping, have to stay indoors. If we have too many smog alerts, people
may decide to move.
It is a balancing act. Now that you know the 2 sides of the equation—consumption and
disposal—you can make a more informed decision.
Information taken from: Agusta et al. ScienceWise (2003). Succeeding in Today’s World. Irwin Publishing