Energy/Electrical Notes
1. Energy is the ability to make things move or change. Energy comes in many forms: sound, light, heat, mechanical energy, and electricity.
2. Electricity, or electrical energy, is the energy of moving electric charges.
a) conductor—material that electrical energy can flow through easily (metals: copper and silver)
b) insulator—material that electrical energy does not move through easily (nonmetals)
3. electric current---flow of charged particles
a) present when charges flow through a conductor
b) current must have a pathway (electric circuit) through which it can move
c) electric circuit—closed path through which current, or electricity, can flow
Ø consists of an energy source, one or more electrical devices (loads), a way to turn the circuit off and on, and a conductor connecting it all (such as copper wire)
Ø series circuits—allows electrons to follow only one path
i. the loads must share the available voltage
ii. each load will use up some portion of the voltage, leaving less for the next load in the circuit
iii. this means that the light, heat, or sound given off by the device will be reduced
Ø parallel circuits—can follow more than one path to return to the source
i. splits up among all available paths
ii. voltage is the same across all paths in a parallel circuit
iii. each device will produce at full output
Ø voltage—electrical energy available for moving a charge
i. batteries—used in wireless devices; changes chemical energy into electrical energy
ii. solar cells—some use solar energy; transform sunlight into electrical energy
5. Electrical Power Grids
a) power generation plants—produce electrical energy from fossil fuels, hydroelectric power, geothermal power, or nuclear power
b) generators—machine that changes mechanical energy (moving) into electrical energy (water heated to produce steam; steam turns turbine that spins the generator)
c) Electricity produced in power plants must be transported to homes and businesses to be useful.
d) power grids—system of wires, transformers, and other devices that carry electric current from power plants to individual users
Ø A grid changes the voltage of the current it carries.
Ø wires carry electricity from the generator to a substation
Ø electricity must travel long distances through a power grid to its destination
Ø use alternating current (AC) in transmission and distribution systems---the voltage can be changed in an alternating current system to transfer energy more efficiently
Ø Example of a path of electricity from a local power substation to an appliance in a home—
s power plant ®substation ® transformers® junction box ® outlet ®TV
e) High-voltage electricity travels from the substation to homes and businesses. Before entering homes, the electricity moves into another substation. In this substation, step-down transformers are used to lower the voltage of the electricity. Once voltage is reduced to the appropriate levels, wires carry the electricity to where it will be used.
f) substation—location that houses transformers
Ø used to change AC voltages from one level to another, and/or change AC to DC or DC to AC (AC = alternating current; DC = direct current)
Ø transformers—device that increases or decreases electric voltage
o step-up transformer—increases voltage
s makes it easier to transport the electricity over long distances
o step-down transformer—decreases voltage
Ø distribution substations---located near to the end-users
o changes voltage to lower levels for use by end-users (industrial, commercial, and residential customers)
g) transmission lines—carry electric energy from one point to another in the power system
Ø underground or overhead lines
h) distribution lines—smaller lines that carry electricity from substations to and throughout neighborhoods
Ø can be underground or on overhead poles
i) A junction box is a box (either plastic or metal) used by electricians to join wires together. They can be located in walls or ceilings and are usually covered by a cover plate.
j) outlets—All electrical outlets in the United States are configured to transmit a charge of 120 volts of Alternating Current (AC). Alternating Current is an electrical current whose direction reverses cyclically. It is believed that this is the most efficient form in which electricity can be transmitted as it is supposed to prevent the loss of excess energy.
Ø Electricity passes out through the hot socket, into the hot side of the appliance's plug, into the appliance, then out through the other side of the appliances plug, and back into the neutral socket.
k) Mississippi Companies--
Ø Power Plants—
o Grand Gulf nuclear power plant (Port Gibson) and Mississippi Power electric plant (Gulfport)--coal
Ø Kuhlman Electric Corporation (Crystal Springs)—major supplier of the transformers for the Mississippi power grid
Ø Howard Industries (Laurel and Ellisville)—supplies electrical equipment for the grid
6. Energy Sources--
a) fossil fuels—remains of ancient organisms--coal, oil, natural gas—nonrenewable
b) nuclear—energy stored in the nucleus of an atom; energy released when nuclei join together or split apart; ¼ of Mississippi’s electricity
c) hydroelectric—energy of moving water
d) geothermal—heat energy obtained from below the Earth’s surface
e) wind—harnessing the wind to produce electricity through windmills
f) solar—radiation energy produced by the sun; more reaches the equatorial regions rather than the polar regions because those regions receive sun rays closest to vertical
The following information was found at the eHow website:
http://www.ehow.com/how-does_5148746_electricity-travel-home.html
· The power is then put through a device called a step-up transformer. When a wire coil with a changing current running through it is put next to a coil without current running through it, the current from the first wire produces a current in the second. If the second coil has more turns of wire than the first, it receives a higher voltage current than the first wire. A set of coils working this way constitute a step-up transformer.
· Voltage needs to be stepped up because it might have miles to travel before it gets to your house. Voltage is like pressure---it controls how hard the electricity pushes. Electric wire is a pretty good conductor, but it resists the flow of electricity somewhat. Having high voltage keeps the electricity flowing efficiently without slowing down or losing power. If the electricity has very far to go, it might pass through a substation, where it is boosted again on the way to its destination.
·
When the electricity gets to your house, it is run through a step-down
transformer. In the United States, this reduces it to 120 volts, but in most
other countries, the electricity comes in at 210 to 240 volts. Either way, the
electricity is at a much safer level then in the electric main. Even if you were
to accidentally get an electric shock from it, it probably wouldn't seriously
injure or kill you. The electricity runs through a power meter that records how
much you use, and then into the fuse box or circuit breaker in your house. From
there, it flows into all the power outlets and built-in appliances.