Math Tips
The information given here is simply the opinion of one guy who did
electrical work from 1967 until 2001and has taught electrical courses
since about 1973. Please confirm all aspects of this information with
others before acting on the contents. Hopefully you will find helpful
details here which will make your career choice easier to follow.
Cheers:>) David U. Larson
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Standard Layout
Organization of data is important to a successful outcome for any mathematical
calculation. My favorite layout is as
below:
Given
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Formula
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Substitution
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Solution
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Given is the place where quantities provided in the problem are listed with
the appropriate symbols. This step is the most difficult.
Formula is the place where the formula which allows the given information to
find the desired answer.
Substitution is where the given information is substituted into the
formula.
Solution is where the calculator is used to find the answer.
Click HERE to see a sample problem completed in this way.
Technique of Solution
All mathematical problems probably have more than one method which can be used
to find the correct solution. When you find a technique which you feel
comfortable using, memorize it. This should be done aloud without reference.
Practice while driving and while waiting at a stop light. Listen HERE to hear a
sample of this technique of solution suggestion for a voltage drop problem.
Estimate The Answer
Mathematics problems are often difficult to apply an estimation. But working
many examples of problems over time will provide a seat-of-the-pants feeling for
the magnitude of the answer. When ever possible, make an educational guess
before crunching the numbers.
Use Check Values
The application of check values to a specific set of formulas will demonstrate
to you if you are applying the formulas and calculator properly. The advantage
of this study practice exercise is to verify that you can correctly apply each
formula. Here's a chance for you to try this. Click HERE to see formulas for AC
circuits taken from my
Reference Formulas Appendix Workbook. Print the page then use these check values
to verify that you can correctly apply each formula.
When you try a formula, substitute the check values into the right side of a
formula. Do the math, and if you get a close answer to the left side of the
formula, you're doing the calculator entry aspect properly. Circle the formulas
which you produce a correct answer. Keep working on any that do not work out.
Seek help of you can not make any of these work. I've used these check values
and formulas for several years. So all problems for several years. So all
problems should work out. You will be slightly off due to the number of places
to the right of the decimal.
Make up your own check values for each formula used to make electrical
calculations.
Calculator Use
The little booklet which comes with a calculator is quite helpful. Don't ignore
it or throw it away. The calculator I recommend for use with all the workbooks I
sell at ElectricianEducation.com is the Texas Instruments TI-30Xa. Note the Xa.
That's the right one. Nothing else. It is about $15 or less. How such a great
calculator is made so inexpensively bafels me to this day.
Texas Instruments has a great web site. Click HERE to visit their site.
Rounding Off
Don't. Leave all digits to the right of the decimal point in your calculator as
you work a problem. Some problems do not need any digits to the right of the
decimal. Like circular mils in a voltage drop problem. Some problems need as
many as four places to the right of the decimal like conduit and nipple fill
problems.
When digits are important to the right of the decimal, use the STO (Storage)
and RCL (Recall) keys feature of the TI-30Xa to maintain accuracy. See the
instruction booklet for calculator technique. Remember, if a formula has more
than one quantity on the denominator, brackets are needed to enter the problem
properly.
Example L = Vd Cm divided by (2 k I ) on the calculator becomes:
Vd times Cm = divided by ( 2 times k times I ) equals answer.
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