Download 01421-2.6 Basic Electrical Terms and Theories

Course:
Unit 2:
01.421
Agriculture Mechanics Technology
Electrical Wiring
Lesson 6: Basic Electrical Terms and
Theories
QCC: .............................................................................................................. 278, 282, 285, 287
Objectives:
1. Describe the theory of electricity.
2. Define electrical terms.
3. Identify electrical symbols used in diagrams and floor plans.
Teaching Time:
2 hours
References:
Understanding Electricity and Electrical Terms. AAVIM, Winterville, GA.
Materials and Equipment:
Power Points:
Electrical Principles and Wiring Materials
Electrical Principles
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
1
Georgia Agriculture Education Curriculum
TEACHING PROCEDURE
Introduction and Mental Set
Electricity is one of the major power sources for houses, farm buildings, and
Agri-businesses. Understanding how this energy source is produced and
delivered to the needed consumer is important. The types of simple wiring
circuit used and how to make minor electrical repairs is useful. The
maintenance of electrical circuits and equipment properly to ensure their long
life and safe operation.
Discussion
1.
Discuss with students the electrical theory of producing
electricity.
A.
Relationship between Amperes, Volts, and Watts
$ Watts=volts x amperes
$ Volts=watts/amperes
$ Amperes=watts/volts
B.
Ohms Law
$ E=Volts
$ I=Amperes
$ R=Resistance
$ I=E/R
$ R=E/I
2.
Explain the following terms on the board and have students
define:
A.
Circuit
I.
Watt
B.
Conductor
J.
Kilo-watt hour
C.
Insulator
K.
AC
D.
Ampere
L.
DC
E.
Volt
M.
Single-phase
F.
Ohm
N.
Three-phase
G.
Current
O.
Flow of current
H.
Electrical pressure
Have an example of each and illustrate if possible.
3.
Have a pre-wired parallel and series circuit to illustrate the
difference.
Illustrate how to read a nameplate on a motor and an electrical tool to
show where information can be found in regard to the defined terms.
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
2
Georgia Agriculture Education Curriculum
SUMMARY
Electrical energy is a useful tool in houses, on farms, and in Agribusinesses. The understanding of how this energy is transmitted from
electrical power plants to the consumer can be important information.
The knowledge and skills learned can prevent injury to people as they
use electrical equipment in their homes and on the job.
Evaluation
Written test
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
3
Georgia Agriculture Education Curriculum
ELECTRICAL TERMS
1. ELECTRICITY- the flow of electrons
2. CIRCUIT- path followed by electrons from and back to the source.
3. CONDUCTORS- substance which permit electrons to move easily.
Examples: copper, aluminum
4. INSULATORS- substances which will not conduct electrons.
Examples: glass, rubber, plastic
5. RESISTANCE- the requiring of energy to force electrons from one electron
to the next.
Determined by: material, size, length
6. OHM- unit of electrical resistance----R
7. VOLTAGE (VOLTS)- measure of electrical pressure----E
8. AMPERE (AMPS)- measure of electrical current flow----I
1 amp= 6,280,000,000,000,000,000 electrons per second
*************DETERMINES WIRE SIZE NEEDED******************
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
4
Georgia Agriculture Education Curriculum
9. WATTAGE (WATTS)- measure of electrical power
*********WATTS= VOLTS x AMPS***********
VOLT.AMPERE- new term for wattage
*********AMPS= WATTS/VOLTS*************
*********VOLTS= WATTS/AMPS*************
Examples:
120 volts x 10 amps = watts
120 x 10= 1200
2400 watts / 120 volts = amps
2400/120= 20
240 volts / 1800 watts = amps
1800/240= 7.5
2400 watts / 10 amps = volts
2400/10= 240
10. OHMS LAW- the electrical current flowing in a circuit varies directly with
the electrical pressure and inversely with the opposition
I=E/R
amps= volts/ohms
11. KILLOWATT- 1000 watts
12. KILOWATT HOUR- watts x hours/1000
13. HORSEPOWER- used to rate electric motors
1 HP- 1000 watts
Theoretical horsepower= 746 watts
******TO CHANGE HORSEPOWER TO WATTS********
1000 WATTS/HP FOR 1/2 OR LARGER
1200 WATTS?HP FOR <1/2
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
5
Georgia Agriculture Education Curriculum
14. DC- direct current-flows in only one direction
15. AC- alternating current-flows in one direction then the other.
Cycle repeats 60 times per second
60 hertz
16. SINGLE PHASE- 1 transformer, 3 wires from pole to house, 2 "hot" 1
neutral, 120 and 240 volts
17. THREE PHASE- 3 transformers, 4 wires, 3 "hot" 1 neutral
used where large quantities of power are needed18. AMPACITY- current rating in amperes that a conductor can carry
continuously without exceeding its temperature rating
19. BONDING- the grounding of all metal enclosures of electrical wiring and
equipment
*non-current carrying parts of the electrical system
*equipment ground provides low impedance path for fault current to flow
back to the system ground
*necessary for over current protection device to operate properly
20. BRANCH CIRCUIT- the conductors between the final overcurrent device
and the outlets
*appliance- 20ampere, supplying outlets for the connection of appliances
*general purpose- 15 or 20 ampere, supply outlets for lighting and
receptacles not in kitchen
*individual- supplies only one piece of equipment
*multiwire- 2 or more ungrounded (hots) with a neutral or grounded
conductor
can serve as 2 separate 2 wire circuits
25% fewer conductors
voltage drop reduced as much as 50 %
reduced conduit size
21. CIRCUIT BREAKER- type of overcurrent protection device
22. CONTINUOUS LOAD- the current is expected to continue for 3 hours or
more
*conductors are rated for 100% continuous loading
*overcurrent protection devices are limited to 80% of the device rating
23. DEVICE- unit of an electrical system that is intended to carry but not
consume electricity
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
6
Georgia Agriculture Education Curriculum
24. DISCONNECTING MEANS- device or group of devices that disconnects
the main power supply conductors
25. FEEDER- the circuit conductors between the service equipment and the
branch circuit overcurrent device
26. GROUNDED- the intentional connection to earth
27. GROUNDING ELECTRODE CONDUCTOR- the conductor used to connect
the grounding electrode (Ground rod) to the grounded conductor at the
service
28. OVERCURRENT- current greater than the rated current of equipment or
conductors
*overload
*Short circuit
*ground fault
29. SERVICE CONDUCTORS- conductors on the supply side of service
disconnect
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
7
Georgia Agriculture Education Curriculum
EXAM
1.
Electricity is the flow of electrons from one ____________ to another.
2.
The flow of electricity is controlled in an electric ________________.
3.
Atoms contain _______________ and _________________.
4.
Each proton has a _______________ charge.
5.
Each electron has a ______________ charge.
6.
_____________ are attached to protons.
7.
The number of electrons and the number of protons are exactly equal
in a _________________ atom.
8.
The continuing flow of electrons is referred to as _______________.
9.
In a light bulb filament, energy is given off as _____________ and
__________________.
10.
Two protective devices that prevent too much current from flowing are
a __________________ and _______________.
11.
Two basic types of circuits are the _________________ and the
_________________ circuit.
12.
Are most circuits in your home parallel or series circuits?
13.
Copper, aluminum and silver are examples of good electrical
_______________.
14.
Five examples of good insulators are __________, __________,
__________, __________, and __________.
15.
The __________ is the unit used to define electric current.
16.
To measure current flow (amperes) you use an instrument called an
___________________.
Important information such as ampere rating is listed on the
equipment _________________.
17.
18.
Electrical pressure is defined by a unit called________________.
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
8
Georgia Agriculture Education Curriculum
19.
How can you determine if three-wire service is supplied to your
house_________________.
20.
The unit of electrical resistance is the _________________.
21.
What are the three factors that determine the amount of resistance
(ohms) in a conductor?
22.
Define Ohms law.
23.
What are the equations used to express Ohms law?
24.
Electric power is measured in terms of _____________.
25.
A kilowatt is equal to ____________ watts.
26.
You may purchase electrical energy in the form of ______-hours.
27.
The two types of current are ___________ current and _________
current.
28.
The type of current that flows in only one direction is __________
current.
29.
____________ current is the type of current that flows in one
direction, reverses, then flows in the other direction.
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
9
Georgia Agriculture Education Curriculum
Exam Answers
1.
place
2.
circuit
3.
electrons and protons
4.
positively
5.
negatively
6.
neutrons
7.
neutral
9.
current
10.
light and heat
11.
fuses and circuit breakers
12.
parallel and series
13.
parallel circuits
14.
conductors
15.
Glass, vinyl, rubber, asbestos, air and wood are all acceptable.
16.
ampere
17.
ammeter
18.
name plate
19.
volts
20.
21.
Single-phase service uses three wires: two hot and one neutral
ground. Three-phase service uses four wires: three hot wires and one
ground.
ohms
22.
length of run, cross sectional area, and temperature of the conductor
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
10
Georgia Agriculture Education Curriculum
23.
Volts equal the amperes multiplied by the resistance.
24.
Volts = E, Amperes = I, and Resistance = R
E = I x R or
I = E / R or
25.
1000
26.
kilowatt
27.
direct and alternating
28.
direct
29.
alternating
R=E/ I
Course: 01.421 Agriculture Mechanics Technology
Revised May 2007
Unit 2, Lesson 6
11