I'm looking for a resource that would explain voltage, current, and that sort of basic stuff well enough that my girlfriend will be able to have some idea what I'm talking about. I don't need a tome, and not looking for something that cutesies it up at the expense of information.
Whenever I've tried to explain it, I don't seem to do a very good job, because I'm into electronics at a much deeper level, and have had an intuitive understanding of voltage and current since I was in first grade and my father gave me a current limited power supply and told me where his pilot light bin was.
I think once she has an understanding of voltage, current, what is meant by voltage drop - after that, I feel like I can take it the rest of the way, and can explain what I'm doing - it's the foundation that I'm having a hard time explaining.
I see it this way; my friend designs clothes. I have no idea how he does this. Whatever he has in his head that allows him to design clothes is completely missing from my head. Likewise electronics the other way around. I know he is incapable of understanding the basics of electronics, yet, to me, it is obvious. Whatever I have that means I can understand voltage, current, power etc intuitively is missing for him. Some people get the basics of electricity easily, some people never will.
(Sadly some of the questions on these forums indicate that some people trying to use Arduino and electronics generally will never get the basics either).
The water analogy is pretty good. Under "normal conditions" the water pressure is present and fairly constant. And, the voltage is present and fairly constant.
With constant pressure water flow depends on resistance.
With constant voltage current flow depends on resistance.
But, but you need to explain a couple of differences -
If you cut a pipe you get zero resistance and water flows-out all over the place. If you cut a wire you get infinite resistance and no current flows.
Nothing bad happens with zero water resistance (except for maybe a flood) but with zero electrical resistance you can get excess current and things can burn-up.
And with electronics we are usually more interested in digital signals & logic, or analog signals and amplification, so the basics of current flow and electrical power are secondary (although still related and important).
We’re all different so we all learn in different ways and for some of us, there is no substitute for active learning. That’s why the pilot lamps with glowing filaments worked for you. Do you have a CV/CC supply and some #47 lamps you could give her?
Seriously, Ive never seen anything online that is worthwhile. That said, I haven’t conducted an exhaustive search either, I just find modern content to be woefully lacking and geared towards the all too common attention deficit disorder brains of the current generation.
IMO, the best references are the 1950-ish textbooks I find at the local thrift store. Clear, concise and coherent. Math, physics, electronics, whatever. If it has a threadbare cloth cover, I’ll pick it up and have a look.
If you can’t get her interested in anything technical, it’s probably a lost cause. You cannot teach someone that has has no interest in the subject material. That’s what makes some teachers so good, they can make the boring interesting.
DVDdoug:
If you cut a pipe you get zero resistance and water flows-out all over the place. If you cut a wire you get infinite resistance and no current flows.
Nothing bad happens with zero water resistance (except for maybe a flood) but with zero electrical resistance you can get excess current and things can burn-up.
If you use the analogy to actually run something like a sprinkler, then if you cut the hose water does go all over, but the sprinkler doesn't work either. (open circuit)
As for the zero water resistance, it has similarities with electronics. The hose is the same as a wire or trace, in which zero resistance is good. It's the load where things go badly. Zero resistance in electronics causes max current (max flow) and lets voltage sag (water pressure drops)
You can also let her think about a garden hose vs a firehose hooked up to a hydrant. Same pressure, vastly different flow.
This is all part of science. Usually - the first step is to provide basic science 'constructs' or theoretical concepts - like 'electrons'. And indicate what science currently describes how they behave, or how they can generally be moved.
And just tell them that being able to control how the electrons move, and how they can be used to control the energy "levels" at different regions or points in an electronic circuit (or electronic system) results in lots of applications for electronics --- and mechanics etc. This includes electronic signalling for electronic communications, control of power and energy in power-systems, storing electrical energy in batteries, generating magnetic fields ----- a whole bunch of potentially useful and practical things.
Could just say electrons are hypothetical little balls that have particular properties or behaviours, which the scientists of physicists have defined, and are able to do many useful things with them. And they can be moved or stored by applying the relevant 'forces' to them. And when these little balls are moving there is a quantity associated with the number of these balls per second. And they have to give this quantity a name.
If they need to understand more --- then it'll be time to upgrade to basic circuit theory books.
The water analogy is quite ok for getting the general idea across for flow through a electrical line. A medium for which to allow the water to get from one point to another. Cut the pipe..... and no water reaches its destination for a general 1 pipe case.... not counting cases like the destination being a bucket underneath the cut pipes.
We know that in circuits.... the electrons flow around a circuit loop.
Restrictions in water has a tendency of raising pressure. Our resistors drop voltage.
Only up to the pressure available from the supply, the same as voltage. Restrictions in water limit the flow and reduce the pressure beyond the restriction, the same as a resistor.
wolframore:
The water analogy always fell apart with resistance for me. Restrictions in water has a tendency of raising pressure. Our resisters drop voltage.
No, resistors generate a potential difference, just like restrictions generating a pressure difference.
MarkT:
No, resistors generate a potential difference, just like restrictions generating a pressure difference.
Mark... it doesn't work in my mind... a compression effect happens with water pipes where you trade flow for pressure. I don't see the same thing happening with electronics.
A resistor output does not raise voltage but affects current.
Am I looking at it the wrong way? I may be confusing water speed with pressure.... velocity... what's that in electronics?
The water analogy works in many ways but this is one where it falls apart for me.
Mark... it doesn't work in my mind... a compression effect happens with water pipes where you trade flow for pressure. I don't see the same thing happening with electronics.
A resistor output does not raise voltage but affects current.
Am I looking at it the wrong way? I may be confusing water speed with pressure.... velocity... what's that in electronics?
The water analogy works in many ways but this is one where it falls apart for me.
I guess that's the problem with analogies, however good they don't quite work for everyone.
wolframore:
A resistor output does not raise voltage but affects current.
This is the thing with theory. In basic circuit theory, the 'ideal' (just a ideal construct) resistor is a component that is associated with the relationship V = I.R (or all expressions directly associated with this.... like R = V/I etc).
It is only later in physics where they start considering real-world components, which have power losses that could often be modeled with resistances, and additional features like capacitance and inductance, non-linear effects etc.
The V = I.R equation just says that if a particular amount of current is already flowing through this ideal resistor, then it will be possible to measure a 'voltage' (equal to V) across the resistor. Or this voltage V can be predicted (if not measured). And if a voltage V is 'applied' (by a battery etc) across the resistor, then the prediction will be that a current equal to 'I' will flow through that resistor.