Have you ever asked yourself what electricity really is?
If we’d go back in time by a couple of hundred years, you would possibly have found these definitions:
“First of all there is static electricity. That is the sort when we get a sudden jolt while touching a door knob or similar object after walking on a carpet. Secondly there is animal electricity. This is the kind which makes a frog leg twitch when certain metals in or around the dead frog are connected. Thirdly, there is the sort of electricity which comes right down from the sky. It can be collected by a kite and makes sparks jump to your hand…”
We may laugh, but that was the way scientists many years ago explained those strange happenings they were so eager to demonstrate.
But there ARE different kinds of electricity, aren’t there? The sparks from a Van der Graaff generator *) or lightning during a thunderstorm cannot be compared to the tiny power lighting up a torch?
Let’s find out.
Take water as an example. Water may appear as ice or snow one day, steam another day. We drink it when we are thirsty, we swim in it. And as water is always water, so electricity is always electricity. It is energy, the movement of electrons. It may be a steady one-way current, (as in the torch light – DC), it may alternate from positive to negative many times a second (for example in your domestic power supply – AC) , or the music signal fed to your loudspeaker (which we call a complex signal), or finally the short but extremely high energy burst released in a lightning strike (a pulse). It may even be stationary. Like a spring that is pulled but not allowed to relax, an object can be electrically charged and then we talk about ‘static electricity’.
The bow and arrow in the drawing above will help you understand the difference between voltage and current.
Electricity has two different values and how strong or weak each of them are depends on where they occur and how they are generated: Tension, or pressure (better still: the Potential Difference between two points) which we call VOLTAGE is expressed in VOLTS. That is one. The other value is the amount, the CURRENT, that is how many electrons are pushed around a circuit by the voltage. And this CURRENT is measured inAMPERES (or Amps for short).
We can calculate both those values and that leads to some interesting experiments, especially if we have some actual parts at hand, and instruments, to verify our calculations. How we can do this we will see later.
Keep in mind that current and voltage values can vary enormously. Arc welding, for example, takes a large amount of current while the voltage is low (maybe some 120 Amps at 80 Volts). On the other extreme we have the sparks from the Van Der Graaff generator. Here we may find up to hundreds of thousands of volts. Sparks may jump over a distance of several inches. They will not kill you. The current is by far too low for that.
But it’s all simply the mysterious and yet so very useful energy which we simply call: Electricity. It is the force that in modern electronics makes all our wonderful gadgets work. In the following ELECTRONICS FOR JUNIORS FACT SHEETS we will examine – one interesting fact at a time (to make it easy for us) – what you can do with it and have fun doing it.
*) A ‘Van de Graaff Generator’ is a gadget that produces extremely high voltages while the current is very low indeed. The voltage creates some fantastic display of sparks. Generators of this type may be found in technical institutions and some electronic laboratories. They should be used only by people experienced in that kind of high-voltage electricity. There are interesting web pages on the net. Search for “Van_de_Graaff”.
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