Basic Terms: Volts, Amps, Amp Hours, Watts, C-Rating, etc

Last Reviewed: Mon, 27/Mar/2017


Using the water analogy to explain basic electrical terms such as Volts, Amps, Watts, and Amp-Hours
Using water as an analogy makes basic electricity easier to understand. Imagine a 100 foot water tower. Its height above a given spigot determines the amount of pressure available at that spigot. A spigot at 100 feet high has almost no pressure, while a spigot at the base of the tower has a lot of pressure. The difference in pressure between two points is called voltage. Now, imaging two spigots at the base of the tower, one with a 1/2" pipe, the other with a 1" pipe. The amount of water that will flow from the 1" pipe is much greater than the smaller one. The measurement of the amount of flow is called amperage. Amp-Hours is a measurement of how much water is in the tower -- how much it holds. Expressed another way:

Electrical Water
Volts (potential) Pressure
Amps (current) Volume
Amp Hours (capacity) Gallons

Leaving the water analogy now.. Watts is the same thing as power. It is always calculated as volts X amps. 2 volts at 50 amps = 100 watts of power. 50 volts at 2 amps = 100 watts of power. 25 volts at 4 amps = 100 watts of power. Simple enough, but there is a reason for different voltages. Amps is a measurement of current flow, and current tends to heat the substance through which it travels. It doesn't take much current to melt a tiny conductor as in a telephone wire. Heat is wasted energy unless you're trying to generate heat, so the larger the gauge of wire, the less energy is wasted in the transport of current. So why don't we use high voltage, low current, and small wires? Well.. voltage can be nasty. The higher the voltage, the more likely it is to jump through an insulator like the sheath of a wire or air. Lightning is very high voltage, so it bridges the insulator (air) to get from the high voltage cloud to the zero voltage ground. Higher voltages are also much more dangerous to humans. That is, no one gets shocked touching the positive and negative terminals of a 12 volt battery, yet the battery has enough power to weld steel. On the other hand, 110 volt outlets in your house will shock the heck out of you and can even kill. All it takes is 1 amp through the chest to stop your heart. A higher voltage makes it easier to break through the insulation (your skin) to get the current to flow.


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