What's a Watt? What's a Volt? A Non-Technical explanation!

[Captain Goddammit]

A lot of burners who otherwise never needed to think about electricity are forced to deal with it in BRC and have asked for help understanding the terms that always get tossed around.
I figured since almost all burners ARE familiar with riding bicycles, I'd try to draw a clear, non-technical bicycle-to-electricity analogy. (I already did this in another thread but electricity comes up so often I think it should be it's own topic.)

The books will tell you Volts x Amps = Watts... but what the hell does that mean?!

You can think of Volts as the electrical equivalent of speed, and Amps as the equivalent of force.
Lets say you're on your bike, going 10 MPH across the playa with a basket-load of fresh ice in first gear - you're pedaling really fast but with low effort. That's kinda' like high Volts and low Amps.
Now switch into 10th gear, carrying the same load at the same 10 MPH. Now you're pedaling hard, at a slow pedal speed. That's similar to a lot of Amps at low Volts.

WATTS is the amount of work actually being done. That's the bike hauling your ice across the playa at 10 MPH. Either high pedal speed and low effort (like in first gear) or low pedal speed at high effort (like in 10th gear) would both result in you and your big ice moving toward camp at 10 MPH.

The POWER (Watts) is the same in each situation described there. High pedal speed x low effort (like when in first gear) = bike moving across playa at 10 MPH.
Low pedal speed x high effort (like when in tenth gear) also = bike moving across playa at 10 MPH.

That's why the formula says Volts (pedal speed) x Amps (pedal effort) = Watts (bike hauling ice).
120 volts x 10 amps = 1200 watts.
12 volts x 100 amps also = 1200 watts.

Lets say you hit a soft silty patch of playa on the way back to camp. To maintain 10 MPH, you need more power (Watts).
You can get it by pedaling the same speed (Volts) but with more effort (Amps).
You can also get it by pedaling faster (more Volts) at the same effort level (Amps).
Both result in more Watts (bike working harder to haul ice through soft patch of playa).

Here's the deal about wire size vs. power being sent through it.
Proper wire size (gauge) is determined more by Amps than by Volts.
Back to that bike pedal crank - if you had a skinny, weak pedal crank but stayed in first gear, you'd have to pedal fast but not very hard. The crank probably would hold up.
If you shift into 10th gear and pedal slowly (low Volts) but push really hard (high Amps), you'll likely bend or break the skinny crank.

That's why Amps determine the necessary wire size, and why the same wire can carry more power at higher voltage/lower amps than it can at lower voltage/higher amps.
That's why the 12-volt battery cable in your car is HUGE wire, but the 120 volt wiring in your house isn't so fat.

About getting shocked: High Volts tend to zap you a lot more than high Amps. You can grab both terminals of your car battery and feel nothing at all... that's only 12 Volts, but a car battery can supply hundreds of Amps!
But touch the terminal of the spark plug wire, even the one on your lawn mower engine, and it'll zap the hell out of you. The engine's "coil" converted the 12 volts way up to several thousand volts, but at low Amps.

My analogy: Someone is pedaling REALLY fast (high Volts). You stick your hand in the way of the pedal. It whacks you!
Now lets say someone is pedaling REALLY hard, but very slowly. Stick your hand in the way of the pedal - doesn't hurt!

There are some gross oversimplifications in these descriptions; if anyone wants to elaborate go for it, but the idea is just to help people who don't understand electricity at all, and don't want to, understand the terms being thrown at them as they try to figure out their camp power logistics.

[ygmir]

[youtube]http://www.youtube.com/watch?v=2CTPLUcQAjk[/youtube]

[dr.placebo]

Apologies for being pedantic, but watts is actually an energy rate. Watts times time is energy.

Maybe converting to money is better. When you get charged for energy usage you get charged for kilowatt-hours. For example, if you are being charged $0.12 per kilowatt-hour, then you are being charged a penny every 5 minutes for every kilowatt you have used for that time. If you have a 1.5 kilowatt hair dryer, and you run it for 10 minutes, then you have used up 3 cents worth of electricity (2 cents times 1.5).

Otherwise I like the bike example.

[ygmir]

Doc:

don't apologize for what you do best..............it's an endearing quality........no, really, it is..............*grin*

[Captain Goddammit]

Apologies for being pedantic, but watts is actually an energy rate. Watts times time is energy.

No it isn't. Watt-hours, like the utility companies charge you for, is energy x time. One watt for one hour duration is a watt-hour.
But a watt is what it is, volts x amps. Has nothing to do with time.

[dr.placebo]

http://en.wikipedia.org/wiki/Watt-hour

[Captain Goddammit]

http://en.wikipedia.org/wiki/Watt-hour

Read that... it tells you exactly what I just did.
A watt-hour is a watt used for an hour's time. A watt-hour is a rate. I was explaining what a watt IS.
Let's use your money analogy. Maybe you work and get paid $20/hr. That is your rate of pay. $20 is not a RATE, it's an amount of value... $20/hr is a rate.
A watt is not a watt-hour.

[Token]

Oh, me, pick me! I got an example of power vs. energy!

If you got a 55 gallon drum sitting on a 4 foot table and the drum has two spouts at the bottom; one is 1/2 inch, the other is 1 inch.

Say you run each spout to a water wheel.

The 55 gallons of water at a height of 4 feet represents the stored energy in the system.

Energy ==> 55 Gallons, four feet potential.
Voltage ==> 4 feet potential.
Current ==> 1/2" pipe or 1" pipe flow.

Each spigot can do the same amount of work since energy is conserved.

The 1/2" spigot can produce half the power of the 1" spigot for twice as long.

Running both spigots at the same time will produce 1.5 times the power but the water will run out 1.5 times faster than the 1" spigot alone.

Etc.

[Captain Goddammit]

Love that! Technically, a one-inch spout should flow more than twice what a half-inch one would because a one-inch diameter circle is more than twice the area of a half-inch circle, I'm only picking that knit before someone says your example isn't right, I know you probably are aware and wanted to keep it simple. The idea is right!

[Boijoy]

ya'll are making my head hurt.

[epic_elite]

cool...

i useful thread to reference for future projects.

[dr.placebo]

The water example is basically correct (allowing for what CD said about the assumed flow rates of the pipes).

We still don't have closure on the terms power and energy. My background agrees with Wikipedia, power is a rate of energy usage, and a watt is a measure of power, and a watt-hour is a measure of energy.

Outside of the terminology, the bicycle discussion is basically correct.

[gyre]

I always found the analogies hopelessly confusing, especially the water pipe one.

Volts is potential power.
Amperage is the amount.
Watts is the total, accounting for variations in voltage and amperage.

And I wouldn't try that battery contact thing.
The only reason you can grab 12 volt wires is that the resistance in the wires and your skin limits the amount of amperage that flows.
That may not always happen with a battery.
There is enough amperage to vaporize a screwdriver in a car battery.


The chinese store (harbor freight) has Volt-ohm-meters for $3 right now and the back light model for $7.
The $7 model is ringing up for $3 here, but I recommend it regardless.
And they have a higher model for $22 with a temperature sensor.
Replace the supplied batteries with duracell alkaline or lithium.
Otherwise I recommend Fluke.
Everyone needs a meter, even if it's only to check remote batteries and find out when your car battery is dying.

[j_cavera]

Watts!? Doesn't everyone measure power in electron-volts per shake?

- Jim

[ygmir]

The water example is basically correct (allowing for what CD said about the assumed flow rates of the pipes).

We still don't have closure on the terms power and energy. My background agrees with Wikipedia, power is a rate of energy usage, and a watt is a measure of power, and a watt-hour is a measure of energy.

Outside of the terminology, the bicycle discussion is basically correct.

.......

[gyre]