We’re considering getting a generator for our trailer, and discussions have revealed that I know jack about electricity and the way we store and use it. Volts, amps (these are measures of how much electricity is there, I think), ohms, joules (these are measures of “resistance”, whatever that is)…wha? How are these different, and what does each mean?
My fiance, who can normally teach me anything, has run up against this like a brick wall. I’m just not getting it.
My level of “what I think I know” about this is this: electricity is the movement of electrons. This movement moves really well along metal, and if you make a wire out of metal, you can move this movement, this electricity, along the wire and put it where you want to use it. This movement of electrons, where I want it, makes stuff I plug into the wall work.
So, correct me where I’m already lost, and help me grok this, please!
Volts measure potential, or how hard the electric current is “pushing” through the conductor. Think of this as the pressure in a water pipe.
Amps measure the amount of electrons passing through a given point at one time. Think of this as the diameter of a water pipe. Bigger pipe at the same pressure means more water passing through.
Ohms measure resistance – resistance wants to stop electrons from moving and converts their motion to heat. Think of this as friction within a pipe. The rougher the inside of your pipe, the harder you have to pump the water and the more it heats up. Conductors are things with very low resistance; insulators have very high resistance.
Wouldn’t it be easier to use something like Wikipedia?
It would take a lot of work to get someone from your level of understanding up to having a reasonable grasp of the subject (which is pretty wide ranging) which would be very inefficient use of time for a custom write up for oner person.
Of course, you might get lucky.
ETA:
For the purpose of getting a portable power supply, what you need to know is the maximum total power consumption of all the items that you would like to use whilst powered by the generator.
This will be measured in watts (kilowatts) and the rating of the generator should be greater than the maximum total of all the devices that you might want to use concurrently.
All domestic generators will be the correct voltage.
your electrical devices have ratings of how much current it uses (A for Amps) and/or how much power it uses (W for Watts).
you need a generator with a greater value for those than the total of the devices that you plan to use. so you need to go and collect values and make a list. somethings you might have on all the time, other things could only be on as long as the total was under what the generator could produce.
So far so good.
Think of electricity as being similar to the water pipes in your house.
Voltage is equal to the water pressure. (How far the water will squirt out of the hose when you turn it on)
Amps is how much water squirts out of the hose (how many gallons)
resistance is just what is says, say a kink in the hose, or the faucet.
If you are looking at generatiors, you are also concerned with watts which is volts X amps 110V X 10A = 1100 watts.
You will need a generator large enough to cover your expected wattage useage plus a safety margin. You can’t put a 2500 watt load on a generator that only produces 1000 watts, you will burn it out.
So the thing to do is add up all the voltages and amps of the various consumers in your trailer (some things might run on 12V in a trailer, others 110) and calculate your load in watts. keep the two voltages calculations seperate. some generators have a 12V out as well as a 110/220 out.
don’t forget you can’t exceed the maximum in either catagory.
Let’s say for example:
110V
AC unit 15 amps 110X15=1650W
2 lights @ 60W each = 120W
1650 + 120 = 1770W
You will need a generator that is rated above 1770 W continous operation
12V
fridge 5A 12 X 5 = 60W
6 lights at 12W each = 72W
60W + 72W = 132 W.
12V outputs are often given in amps, in this case divide by the voltage (12) = 11Amps.
So the DC output of your generator would need to provide at least 11A continuous for you to be able to light everything up.
Exactly. I might get lucky. I’ve read the wikis on several topics related to this (like the units mentioned), and I’m not gettin’ it. That might be because I’m an idiot or my brain simply isn’t wired (heh!) for this topic, but it might be because I haven’t found the right teacher for me yet.
And if there’s one thing the Dope is full of, it’s awesome teachers - some of them are paid for it and some of them are just people who are great at explaining things. I’m hoping one of them is sitting around bored on this holiday and would be willing to take a stab at it.
friedo and Rick, thank you! That helps a bit. I was lost at a previous metaphor of Volts as “the bucket” and amps as “the water”, because then when told that a large voltage and small amperage was more deadly than a small voltage and large amperage, I got lost. (Wouldn’t the bucket just run out of water faster?) Your analogy of a hose helps my brain. A small amount of water *pushed *through a pressure washer would hurt a lot!
That’s a pretty good summary, what else is it that you want to know?
What I can add is that we can get electrons in a wire to move by spinning a magnet around it. To get enough electrons moving in order to power a city you would need really big magnets that are hard to move. The debate over energy policy is really all about how we can move magnets around wires.
Most of the time we push magnets using steam. We get steam by heating up water, which we can do through nuclear energy or burning coal. Other times we can push magnets using water or wind.
Solar energy involves something completely different than magnet pushing. I don’t know how that works.
Woah. Really? That’s really cool. I had no idea that’s how, fundamentally, electricity is made. So the steam from burning coal or nuclear reactions or a windmill or a hamster running a wheel just…spins magnets? How cool is that?!
So…how do potatoes make electricity? I remember wiring a potato up to a light bulb when I was a kid and it made it light up. No magnets there, so something else must have been moving electrons through the potato and into the wire…
A Battery and a Generator produce electricity in different ways. Batteries use chemical reactions as electron pumps - Generators use moving magnetic fields. You have created a simple battery (more precisely, cell) with your potato and wires.
Wait, wait…back up a minute. Batteries *produce *electricity? I thought they just stored electricity that was made elsewhere…
Or is there more than one kind of battery? Do rechargeable batteries produce electricity or just store it? If they produce it, then why does it need to suck electricity out of my wall socket?
Batteries change chemical potential energy into electrical energy. A Primary (non-rechargeable) cell “uses up” it’s chemicals when producing the electricity. A Secondary (rechargeable) cell uses reversible chemical reactions which allow it to be recharged from another source of electricity.
BTW, Capacitors store electricity which was produced elsewhere. Contrary to what some people think on this board, they are NOT batteries.
batteries store energy in the form of chemicals. these chemicals will react with one another to produce electricity when a wire provides a path (this chemical reaction takes place only slowly without a wire, that is what happens when a battery slowly goes dead).
rechargeable batteries have chemicals that can be restored by recharging.
Well, the potato provided the “electrolyte” that was necessary to cause the dissimilar metals to react. It’s really the metals that are the necessary components. Volta (sound familiar?) made the first battery using Copper and Zinc, and salt water as an electrolyte.
Also known as the Hydraulic analogy, except Amps should be a rate of flow, not a pipe diameter.
Reading the start of this wikipedia article, and the concluding part on possible misconceptions one could get from the hydraulic analogy is a good starting point to really grok electricity.
There was some (small) chemical reaction going on in the potato that moved electrons?