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

Standard Layout
Organization of data is important to a successful outcome for any mathematical calculation. My favorite layout is as below:               









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 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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