Monday, June 28, 2010

Lesson 18: Technician Class Exam Prep T5D

Welcome back!  Here is lesson 18 which covers the T5D questions from the exam question pool and is entirely devoted to Ohm's law.  If you haven't memorized or know how to use Ohm's law yet, you will after this lesson.  Ohm's law basically states that voltage, current, and resistance in a circuit are all related.  The formula is E=IR where E is voltage in volts, I is current in amperes, and R is resistance in ohms.  From the word problems on the exam, you solve the equation for the variable you are looking for and just substitute in the numbers.  There is a decision circle which helps solve for each variable quickly.  It looks like this:
To solve for voltage, current, or resistance, you just cover the letter you are looking for and what remains uncovered is what you need to calculate.  For instance, if you are looking for resistance, you cover the 'R' in the circle and what you are left with is E/I.  So divide E (volts) by I (amperes) and it will give you the resistance in ohms.  Simple?

If you have any questions, comments or suggestions, please feel free to leave them in the comments box.  Until the next installment...



  1. To make this one as easy to remember as the other formula "P=IE" (pie) for calculating power, current, voltage - I use "ear" E=AR.

    As long as you remember that Voltage is "E", and "A" is for Amps (also "I"), it helps to remember the formula.

    Thanks for your video lessons. I am an Extra class operator and am using your CW videos to learn the code. Excellent stuff.
    Dave, KK4EVP

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