22 February, 2002
ELECTRIC MATH !
Tom Curran is the Palmer Station electrician. Tom is from Burlington, Vermont, where he is a member of the International Brotherhood of Electrical Workers, Local 300. Tom is a licensed electrician with over twenty years experience.
This is Tom's first season on the ice. The summer season is a time for maintenance and repair of things having to do with electricity. New construction is done during the winter season, when fewer people are here.
Tom says that math comes into play with an electrician's first license. An electrician uses math all the time. He or she needs to know geometry in order to make angle measurements for bending conduit. An electrician needs to know how to use equations. For example, it is important to know Ohm's Law. Then an electrician can use it to calculate amperes, horsepower, and kilowatts. An electrician also has to be able to read tables and graphs.
The electrician here at Palmer Station also needs to be ingenious. He has to be able to solve many kinds of problems. As Tom said, "You can't just run out to a hardware store if you need a switch and you don't have it!
Tom gave me some math problems. Here they are:
Ohm's Law states that "the rate of the flow of the current is equal to electromotive force divided by resistance.
Electromotive force = volts=E
Current = amperes = I
Resistance = Ohms = R
Watts = P
1) Amperes (I) = Volts (E) divided by Ohms (R)
So, when Volts and Ohms are known, use I = E divided by R
Find the current of a 120 volt circuit with a resistance of 60 Ohms
2) Amperes(I) = watts (P) divided by volts ( E)
When watts and volts are known, use I = P divided by E
A 120 volt circuit has a 1440 watt load. Determine the current (amperes).
3) To find kilowatts in direct current, use this formula:
Kilowatts = volts times amperes divided by 1000
A 120 volt (DC) motor draws a current of 40 amperes. Determine the kilowatts.
4) Tom is putting conductors in a metal box. He wants to use Number 18 wire. According to the National Electric Code, he needs a metal box with a capacity of 30.3 cubic inches in order to place the number of conductors he wants to use. Which of the following box dimensions would be appropriate for this job?
A box 4 inches by 4 inches by 1 ¼ inches.
A box 4 inches diameter by 1 ¼ inches deep.
A box 4 inches by four inches by 2 1/8 inches.
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