# A new way to teach Ohm’s Law?

I’ve been trying to come up with some short videos that I could post on YouTube that would go over the same material that I do in my one-day Tech classes. In my classes, I basically teach the answers to the questions, but I also try to give a little bit of context, so that they get some idea anyway of the bigger picture.

I start out with the day with electrical principles. That means talking about questions in section T5. Obviously, Ohm’s Law is a big part of section T5. So, I searched YouTube to see what other videos are already out there that explain Ohm’s Law.

In doing this, I ran across a video by a guy named Daniel Sullivan. Apparently, he teaches classes for electricians and industrial technicians. Here’s his video, “Teaching Ohm’s Law to Techs – Part 1″:

One of his main points is that we shouldn’t use the notation E, I, and R when talking about Ohm’s Law. Instead, he says, we should use the notation V, A, and ?. These are, after all, the symbols that we use to denote the units of voltage, resistance, and current, and the symbols that  you see on a meter. If you buy that logic, then the answer to question T5D01 which reads:

What formula is used to calculate current in a circuit?

should be:

Current (A) equals voltage (V) divided by resistance (?).

The more I think about this, the more I like it, and I’ve just e-mailed the Question Pool Committee to see what they think about this. I’d like to know what you think, too.

1. No, that’s a bad idea. There is an important concept here, which is that quantities and units are not the same thing. Voltage, current, and resistance are physical quantities. Volts, amps, and ohms are units. The symbols we use reflect that. E, I, and R represent quantities, while V, A, and ? are units. (Admittedly, V tends to do double duty as the symbol for both the unit volts and the quantity voltage, but they remain different concepts.)

This is important for several reasons. First, Ohm’s law holds true for any consistent set of units. I can use milliamps, megohms, and kilovolts, and E=IR remains true. I don’t have to learn another equation, kV=mA•M?. I can use statvolts, statamperes, and statohms, or abvolts, abamperes, and abohms. The equation remains true.

Correct use of units is high school science. I don’t think it is too much to ask of people who are already learning other material of comparable difficulty. I appreciate your dedication to teaching new hams, but changing the exam material to remove critical concepts is not the right approach.

2. Bob, KG6AF says:

Very interesting video. I’m always fascinated by teachers who not only convey information, but try to think critically about which teaching techniques work and which don’t.

Regarding notation (E/I/R vs. V/A/omega), it all depends on what you’re expecting of the student after they learn Ohm’s Law. If the only goal is to pass a test, then, yes, V/A/omega is easier to memorize. But if we’re trying to give students a foundation on which they can build their knowledge of electronics, then it’s better to teach them notation that they’ll encounter as soon as they read an article in QST, or an electronics textbook, or just about anything that takes them deeper into the field. Even if a student wants nothing more than to occasionally debug a simple piece of equipment, it’s likely they’ll have to read something to tell them how, and that something will use E, I, and R. (In a similar vein, I could make the argument that it’s more intuitive to teach electron flow than current flow, but at the price of being incompatible with virtually everything else written about electronics.)

As for the argument that voltage/omega = amps is more intuitive than voltage=amps x ohms, I guess that’s true, although you could just as easily–and correctly–argue that shoving current through a resistance results in a voltage drop. The volts/omega thing is more intuitive only because every electronics newbie knows about voltage sources, e.g., batteries, but few have heard of a current source.

Oh, and if there’s one Ohm’s Law teaching technique I’d like to drive a stake through, it’s Eagle-Indian-Radio.

3. Dan KB6NU says:

Well, I’m just about convinced that we should stick with the notation E, I, and R, although as Stephen points out, I think that more often than not, you’ll find V used in articles and technical papers than you will E.

As far as teaching the concept, I do think that starting with the I=E/R form of the equation makes the most sense in terms of what’s going on in most circuits. The reason for this is that the majority of the time we’re working with a fixed power supply voltage.