Finding Ohm's Law
/In 2014, Comedian Lewis Black was invited to the national press corps dinner. Although incredibly funny, Black’s comedy is political and profanity-laced, he also leans to the left just a bit. Considering he was performing with Dick Cheney sitting next to him and apparently journalists and politicians don’t like profanity. He was in a little bit of a pickle with his act. He described distilling, sanitizing then writing his act for the Washington press corps as taking thirty years of performing, politics, and profanity then distilling it into one lengthy 20-minute knock-knock joke.
I found meaning in this parable. For AST training we are required to do a five-minute presentation on something. I drew OHM’s law. I thought about Mr. Black’s experience in trying to change his act as I was trying to find the right words to do the presentation. Not as much the political or profanity part, I wish, but how to take something relatively dull and make it interesting. The only thing less exciting than presenting Ohm’s Law would be a three-hour discussion on the dispersion and cleaning efficiencies of espresso cleaning solutions.
Water is the most common analogy when training on electrical concepts. I decided to stick to the water analogy. I was going to take it to the next level. I was going to draw a comparison between Ohm’s Law to Noah’s Flood and God’s wrath. Noah being voltage, the flood being current, and God’s wrath was resistance.
This idea went nowhere fast.
Ohm’s law is an incredibly simple yet elegant equation explaining the relationship between current, voltage, and resistance. Ohm's first law sometimes called the acoustic phase law or simply Ohm's other law states that a musical sound is perceived by the ear as a set of several constituent pure harmonic tones. This is not quite true.
With Ohm’s electrical law he found something that worked. His law states that there is a direct proportionality between the potential differences (voltage) applied across a conductor and the resultant electric current.
To go back to my poor analogy. Noah would be voltage. Noah’s ark has the potential to float, the flood is how much water will it wail take to float the ark and resistance is will god’s wrath resist a flood or will he let it pour. I hope you are no longer wondering why I gave this idea up.
To simplify the concept - Ohm’s law is how the speed of electrons travel around a circuit are influenced by how fast they are being pumped and how much they are being slowed down by blockages
Then we have this. The formula:
I is current. The unit is an Amp. It is defined as the rate of flow of electron in a circuit- current is expressed as an (I) because (C) is used to express the electrical unit of the coulomb
V is voltage, its unit is a Volt and it is It is defined as the potential difference between two points in and electrical field
R is resistance - the unit is an Ohm it is it defined as the opposition that a substance offers to the flow of electric current.
P is power – expressed as Watts. Power is the rate at which the work is being done in an electrical circuit. We’re going to just ignore this for right now.
With Ohms Law, It’s vitally important in describing electric circuits because it relates the voltage to the current, with the resistance value moderating the relationship between the two. This formula applies to heaters, valve coils, motors, light bulbs, etc. The formula makes sense when applied to a specific system in a machine. The best example of practical use is heating element efficiency testing. We have a heater element that we know should create 2.5kW when heating at 208V AC. With the formula, we can calculate what the resistance of that heater should be. (208*208)/2500=17.3. If we check the resistance of the heater and it’s not within +/- 10% then I have a problem with efficiency.
Mortimer Adler once said, “The person who says he knows what he thinks but cannot express it usually does not know what he thinks.”As you learn new things and master new concepts remember there is a difference in knowing something and knowing the name of something. It’s important as you learn as a tech you have an understanding of how the concept works versus knowing what the concept is. Sometimes it’s simple as practice and demonstration, sometimes you learn it in a round-about way, maybe from an oddly philosophical essay on finding ohms law.