Electrical – Amperage and Voltage Question: The Water Pipe Analogy

amperagevoltage

Since Voltage is like water pressure, and Amperage is like the volume of water being pumped, in a given hose (wire), there's a volume threshold based upon its diameter (AWG), but only in relation to the pressure applied (V).

So, if I pour water into a closed end hose, it will fill up and spill out. There is very little or no pressure at all. Just gravity.

If I add pressure, I create friction, the hose expands by resisting the pressure (light slowly fades in). Of course, it's a hose, and it has water in it, and therefore it probably won't catch on fire from friction. If I add too much pressure for the hose (AWG) it will burst. If it was a wire, it would heat up and turn into a light saber, which would be great for an oven, or a foam cutter, or a distant galaxy far, far away.

Am I on the right track?

So, the relationship between applied current and burning your house down correlates to the thickness of your wire (whether it's solid or stranded, what material it's made of, etc.,) and the amount of current you apply to that wire.

QUESTION PART:

Where I'm confused is how amperage works. In a hose, or a water line, for example, each outlet valve reduces the volume of water being sent to the next valve until the pressure is reduced to nothing. If we want the pressure to remain constant, we would need to reduce the pipe diameter as the line continues.

In electricity, it seems like it's similar, only the electrical devices draw amperage…yes? Wouldn't that be like adding a pump to the main water line to pump already pressurized water out of the pipe, in which case, if we did, we may deplete the water line too quickly, causing it to collapse…

Is that what's happening when we fire up too many devices that draw more amperage than the breaker can handle?

Best Answer

Don't forget: the water analogy requires closed loops of pipe. No water pours out anywhere. No pipes change their diameter (no inflation or deflation.) It's not like a long cup of water. It's more like a rotating wheel.

An electric circuit is a ring of pipe, full of water, with no bubbles allowed. Next, add a constriction, and that's a resistor. Add a water-pump into the ring, and that's a power supply. The speed of the water is proportional to amperes, with fast rotation being high current. Voltage is the pressure-difference found across the resistor (or across the pump.) DC is when the water moves continuously. AC is when the water wiggles back and forth (yet notice that any resistor heats up, regardless of the flow-direction.)

Parallel circuits are when we add a couple of "T" junctions to our water-ring, so the path splits at one point, then recombines at another.

A similar electricity analogy is the bicycle wheel, where the rubber of the tire becomes the electricity found inside a closed circle of wire. Push the tire with your hand, so that it spins, and that's the power supply causing a current. Rub the spinning tire with your thumb, and that's a resistor. Mechanical energy flows almost instantly, going from your pushing-hand to your rubbing-thumb. The current starts everywhere, all at once. But the path of current is a closed circle, with no rubber being consumed. And, the electrons (the rubber) move slowly, moving like a wheel.

Electricity isn't a "form of energy," any more than the rubber of a tire is a "form of energy." The electricity (and the rubber) were already there, ever since the circuit was created. And, whenever electricity flows, it goes in a complete circle, with none being gained or lost. Your hand doesn't generate electricity, instead it just causes the existing electricity to start moving. (And in the water-hoses, the pump doesn't generate any electricity. It just takes electricity in through one terminal, while spitting electricity out the other terminal at the same time.)