@edlee Yep, but of course, depends how you look at it. The next step is how to run the numbers in series, parallel, and mixed series/parallel.

Posted by: @binaryrhyme

@edlee Yep, but of course, depends how you look at it. The next step is how to run the numbers in series, parallel, and mixed series/parallel.

Erm.. You've lost me there, that needs explaining.

All I know is, if you know 2 of the values then it's fairly easy to find the 3rd.

@edlee That's true - and the graphic is just a memory aid for how the formulae can be re-arranged. Take V=IR, and to re-arrange to find current, divide both sides by resistance, and you get I (current) = V/R.

The parallel vs series stuff requires a bit more thinking. 

This fellow does a pretty good walk through.

Ohm's Law - YouTube

Hi, I watched the vid on Ohm's law and I get that. I now understand how it works.

I then watched his vid on serial and parallel circuits and I got a bit confused but I will watch it again 'til it sinks in.

So 'V' is Voltage, 'R' is Resistance. So why is current 'I'? Why don't they use 'C'?

It is I for intensity (originally en francais, "intensité du courant") - although I prefer "I felt that one!" 😉

@edlee

Yes I is for Intensity of current measured in amperes. I used to confuse current with currents in the river but it more like gallons per minute. The amount of electricity flowing past a point in the circuit.

C is used for Capacitance (measured in farads) which is the complement of Inductance (measured in henrys) and uses the L symbol.

Voltage is the unit of measure for electric pressure (or force). This is measured between two points.  So a 12 volt battery has an electric pressure of 12 volts between its terminals.

Two identical batteries (electric pumps) in parallel provide the same voltage but between them store twice the amount of electricity to be pumped out. Identical batteries in parallel provide twice the pressure between their shared terminals. Resistors in series are simply like a single resistor extended so the resistance simply adds up. Resistors in parallel provide more pathways for the electricity to flow so less resistance overall between their shared terminals.

I found physical analogies helped me visualise these basic electrical concepts.  Turn on a tap (faucet) and put your finger on the outlet so you can feel the pressure (volts). See how much water comes out in a given amount of time, that is amperes.  And so on for the other electrical concepts.

@robotbuilder My analogy is that of a contour map of a hill. All identical voltages measured from ground are the same height on the hill, and voltages between points other than ground are the differences in height of those two points. You roll faster down a steep slope, and different values of resistance have different frictional characteristics.

It's just an analogy of course. At the end of the day you eventually move beyond it, especially once you bring inductance and capacitance into the mix. 😉

@edlee
Typo:
Identical batteries in parallel provide twice the pressure...
should read,
Identical batteries in series provide twice the pressure...

@binaryrhyme

It's just an analogy of course. At the end of the day you eventually move beyond it, especially once you bring inductance and capacitance into the mix.

You move beyond it with the maths but it helps to visualize the concepts involved.

As for inductance and capacitance I also used analogies and anyway you measure them by how the voltages and amperes change.

An inductor is like a water wheel. It takes time to start turning when pressure is applied storing energy and time to stop turning when pressure is released thus releasing energy. The turning is kinetic energy stored, an analogy with energy stored in the magnetic field.

With capacitance that is a rubber sheet in the pipe that can stretch when pressure is applied and stores energy in the stretched rubber sheet which is released when the pressure is removed, an analogy with energy stored in an electric field.

Then there is the transformer. It is like a lever or two gears. This allow you to visualize how the voltage out can be different to the voltage in but the electric power (watts) remains the same (apart from frictional loss).

@robotbuilder Nod. Capacitance and Inductance complicate the math because they introduce the aspect of changes over time, but for a lot of what we do on the DIY front, Ohm's and Kirchoff's laws get you by. 😉

Yep.. the math, and a little basic physics will get you... through I found that in large systems found in industrial applications, it's always back to the basics to trouble shoot the problem..you can't fix what you don't understand, so we had to know how the process works. Basic electronics was all that most of the techs knew, but we had constant training on PID controls, Fuzzy logic ,  cascade loop control, remote set-point. and a lot of how the process actually is suppose to work..For that we had P&ID, loop schematics, electrical line and logic dwgs. But even with all that, it mostly came down to your training on how to troubleshoot.  Math and physics will only take you so far, and your intuition and years of experience is what most likely solved the mystery....

@inst-tech 

My Dad used to say that experience is what you get when you don't get what you want 🙂

For me, trouble-shooting often seems to be the process by which my subconscious recognizes a mistake I have made in the past. Then all I have to do is try to remember what I did to fix it.

@will “We do not learn from experience... we learn from reflecting on experience.” ― John Dewey.

Alternatively: “Some people have 20 years experience, some have 1 year's experience, 20 times." - Stephen Covey

Or, my favorite tale (of someone I knew) is of a manager who ran a three year, 20 million dollar project that ultimately failed. When the project was shut down, his boss called him in, and he expected to be fired.

"Why would I fire you? I just invested 20 million in your education."

@Will, & @binaryrhyme...

So true..experience is what you get when things go wrong!...lol

And yes, having been involves in several over $100 million projects in my 49 years, I made my share of mistakes.... the learning curve was pretty steep in the beginning, but after about the first 10 or 12  years, it started to click. We in the trade didn't really consider a tech to be a journeyman until they had at least 10 years as a first class tech, so that meant that they had at least 14 years to start...(4years apprenticeship + 10 years as a first class tech) When you combine all the different systems we had in the plant, we had over 30,000 instrumentation of various type, 4500 automated control valves, 6000 motors , 3 DCS vendors, 7 PLC vendors and more than a few analyzers.   lots to keep you busy learning..and making mistakes..

Indeed, reflecting on your mistakes, and remembering what you did to fix it was the key to solving the mysteries that came up on a daily basis..there is absolutely no substitute for experience.. no matter if you have 20 years, or doing it 20 time in a year...lol

@binaryrhyme

When I learned electronics it was with tubes and voltage was abbreviated "E". It wasn't until later that it seemed to be changed to V. I was told it was changed so it wouldn't get confused with one of the elements of a new device called a transistor with element "E" for "emitter".

@iceman Hah. I missed that timeframe, lol. Very interesting. 🙂