- All objects have a charge.
- This charge can be positive, negative, or zero. (Zero charge is called "neutral")
- The electric force works as follows:
- Opposite charges attract
- Like charges (i.e. charges of the same sign) repel
- There is no electric force if either charge is neutral.
- Like the gravitational force, the electric force exists everywhere.
However far it seems
We'll always be together
Together in electric dreams
We have covered the gravitational force, which attracts objects together (due to their mass).
As it happens, there is another force much like the gravitational force, but is a million billion trillion trillion times stronger.
This force is the electric force, which acts on any object with a charge.
All objects have a property called charge (in the same way that all objects have a mass).
Charge can be positive, negative, or zero (unlike mass, which cannot be negative). For example, someone's hair might be positively-charged, a balloon might be negatively-charged, or a mug might be neutral:
Most of things you see around you are probably neutral, but there is a way to make some of them charged — we'll investigate this in a few pages time.
The electric force works as follows:
- Opposite charges attract each other
- Like charges (i.e. charges of the same sign) repel each other
Note how there is no electric force if either charge is neutral. A neutral charge is like a bland person: no-one's attracted or repelled by them. Not even other bland people.
Like the gravitational force, the electric force exists everywhere in the universe. It's a big deal!
The electric force exists everywhere and is much stronger than the gravitational force. So why isn't it very noticeable? It's clear that gravity is everywhere around us, but the electric force isn't apparent in day-to-day life, except in a few specific cases.
The reason we don't notice the electric force much is because it's so strong that any loose plus (+) charges will be attracted to any loose minus (-) charges. Together they form one neutral object, which the electric force doesn't act on. The strength of the electric force is why most of the things around us are neutral!
Here's an analogy: World of Warcraft is a very popular and very addictive game, yet I've never actually met anyone who plays it. Why is that? It's because WoW is so addictive that anyone who plays it never leaves their PC — so you're never going to meet any WoW players in real life.
Charge is measured in the unit of Coulombs:
A positively-charged object might have a charge of +3C, and a negatively-charged object might have a charge of -5C. All neutral objects have a charge of 0C.
One Coulomb is actually a very large amount of charge — it takes 6 quintillion electrons to have a charge of -1C!
Here's a vaguely interesting fact: Charles-Augustin de Coulomb (whom the Coulomb is named after) has his name engraved on the Eiffel Tower. How French.