Monday, July 15, 2024

What is the difference between electric field, voltage and current?

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I hope that you are never in a situation where you are in danger from a downed but energized power line. However, if this happens, the recommended safety procedure is to walk away with tiny not mixed up. This type of movement will keep you from being shocked.

Of course, the best option is to simply avoid this type of dangerous situation, but this is also an opportunity to talk about the important physics of why small steps are the best. We will talk about three big ideas: the difference in electric potential (voltage), electric current and electric field. Yes they are all related, and I will show you how with water and an LED. It’s a great physics demo, but I need to go over the very basic stuff first.

Electric power

It might be better to start with the electric current. It might be the easiest to figure out. It all starts with electrical charges. For just about all electrical interactions in real life, there are only two charges. These two charges are the positively charged proton and the negatively charged electron. Although these particles have different masses, they have exactly the opposite charge. The two particles have a charge magnitude of 1.6 x 1019 Coulombs (the unit of charge). This value appears in other situations, so we call it the fundamental charge and represent it as “e” (short for electron charge). Say you have a long cylinder made of a metal like copper (aw). Each atom of this metal has 29 protons and 29 electrons so the entire wire has zero net charge. All of these copper atoms in the material interact with neighboring atoms in a way that allows an electron to move easily from one copper atom to another (we call these free electrons). When a material does this, we call it an electrical conductor. Essentially, all metals are conductors.

A good model is to think of this wire as a group of positive charges (protons) that are stuck in place with an equal number of negative charges (electrons) that can move. But still, the overall thread is neutral. Now imagine that all these free electrons are moving in the same direction, that is, an electric current. It is the flow of electric charges.

Illustration: Rhett Allain

If you could look at a single point on the wire and count the number of moving electrons (with velocity ve) which exceed it every second, it would be the electric current (I). As an equation, it looks like this:


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