Laws of Electricity for the Layperson

The laws of electricity can be daunting for the uninitiated, to put it mildly. The concepts of voltage, currents, resistance, load, charge etc. are too confusing to be able to differentiate easily and conveniently. The idea to explain it using an analogy came up when an acquaintance enquired about the rating of an Invertor and seemed to be hopelessly confused about the VA ratings and voltage levels and asked whether the output voltage that you get with a higher ratings invertor are higher than the one you get with a lower ratings invertor (ratings are in VA).

Without beating around the bush too much, let’s dive in, with the aid of the analogy:

The figure on the left (Hey, I am not an artist, even if you stretch it) represents a water tank, at a height, H, from the output. The tank has a certain water level, is a cuboid and the pipe has an adjustable stopper.

Now bear with me for a while and assume the following (It shall all be clear in a moment):

  • The amount of water in the tank is the charge
  • The height ‘H‘ is analogous to Voltage ‘V
  • The Stopper represents Resistance
  • The diameter of the pipe is conductance( reverse of resistance
  • The Flow of water represents Current

Now the following scenarios can be considered and explained away

  1. The speed of water flow, all other things being same, depends directly upon the height of water. If the tank is placed very high, high pressure gradient shall cause faster water flow. Analogously, higher the voltage, higher is the current.
  2. The wider the pipe, more water will flow. Conversely, more the stopper obstructs the flow of water, lesser is the water flow. Analogously, the flow of current depends directly on the conductance.
  3. If you are using the water flow for moving the turbine or for doing some other kind of work, it would be dependent upon both the amount of water flowing and on the height of the tank. This is similar in principle to using dams to make electricity. This can be understood to be parallel to the electrical power, VA (which is equal to watts for DC but is greater than or equal to watts for AC, for reasons that cannot be explained using this analogy, unfortunately).
  4. Do you know that the static charge on the body, when you are wearing synthetic fibre and getting out of a car seat on a low humidity day is as large as 21000 Volts, according to some sources(Source: http://amasci.com/emotor/voltmeas.html)? Then why doesn’t it kill us? The wall outlets, that have 230/240/110 volts in various parts of the world do have electrocution hazards, but 21000 Volts static discharge doesn’t? Why?
    It is just that the water in the tank is too little to wet you, no matter how high it is placed. The charge content in a static discharge is too low to make a fatal current flow through the human body.

Of course, the analogy can be further stretched to explain Kirchhoff’s current and voltage laws (KCL and KVL for the EEs out there), but I’d let it rest here.

I hope it clears some confusion.

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One Response to Laws of Electricity for the Layperson

  1. mahendra agarwal says:

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