Understanding Basic Electrical Concepts – The Drain Pipe Analogy

Voltage, Amperage, Ohms, Henrys, Joules, Watts – there are many different and confusing terms related to electricity and for anyone who hasn’t  specifically studied these concepts in school it can be a bit overwhelming. Each term represents a specific element of electrical theory with associated laws formulas which can be very difficult to grasp. A good way to begin understanding a new concept is to have it relate to something already known and understood. In electrical theory one of the most commonly taught is the Drain Pipe Analogy, which compares an electrical system with a hydraulic one as both share many characteristics. In this analogy, three terms are covered – voltage, resistance and current – the three parameters of Ohm’s Law.

How the analogy relates to Voltage

Imagine a water tank and connected to the bottom you have a drain pipe. The water tank itself will represent the amount of charge we have and the pipe the conductor such an insulated copper wire. In our electrical system the “tank” can be an energy source such as a battery or the main power coming from our electrical service. The water pressure at the end of the pipe will be greater with a larger water tank and less with a smaller one. In our Drain Pipe analogy this pressure difference represents voltage because voltage is the measurement of a difference in charge between two points.

How the analogy relates to Current

Just as voltage is compared to water pressure, electrical current relates to water flow. With this in mind the higher our water pressure (voltage) we have the more flow we have (current). Which in our electrical system is more energy being supplied by the source. This current is measured in Amperes, and just like how we measure flow in a time measurement (gallons per minute or GPM) amperes are also measure in a time equation. Specifically, the number of electrons -measured in coulombs – passing over a certain point each second.

How the analogy relates to Resistance

So, what happens to our hydraulic system if we use a narrower pipe to transport our water? It makes sense that you cannot have as much volume of water go through a smaller space as opposed to a larger one. This is how resistance is understood through the analogy. Resistance in a system will reduce the electrical current (amperage) in the circuit even with the pressure remaining the same (voltage).

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