Electricity Basics
Electric Charge
Charge, like energy, is a fundamental principle in Physics, in that it can not be created or destroyed, only transferred between objects.
Charge comes from the subatomic particles found inside atoms. The atom is made up of protons and neutrons (found inside the nucleus), and electrons (found inside the orbitals/shells). The protons are positively charged, the neutrons are neutral and the electrons are negatively charged. |
The charge on the proton and electrons are called the elementary charge, which is equal in size but carry the opposite sign. Since the these charges are so tiny, we usually talk about charge using a bigger unit of the Coulomb.
Elementary Charge Symbol: e Units: Coulombs Amount: +/- 1.6x10^-19 C Charge Symbol: Q Units: Coulombs (C) This means that it takes 6.25X10^18 elementary charges to make one Coulomb. |
From our understanding of chemistry we know that it is usually the electrons (negative charges) moving in a circuit to create electricity. This flow of electrons is called a current. It is defined as the amount of charge that passes through a point every second.
Current
Symbol: I
Units: Ampere (A)
Current
Symbol: I
Units: Ampere (A)
Working with Elementary Charges and Charge
One way to think about elementary charges and charge is to picture a jar of lollies. A set amount of lollies fit into the jar.
If someone gave us a bowl of lollies we could work out how many jars of lollies were used to fill the bowl. Example No of jars = (no of lollies in bowl) / (no of lollies that fit into one jar). We can use this same idea to work out how many Coulombs are present with any amount of elementary charges (or electrons). Remember: there are 6.2 x 10^18 elementary charges in 1C. Example No of Coloumbs = (no of electrons) / (6.2 x 10^18) |
Electrostatics vs Electrodynamics
Electrostatics is the study of stationary charges, whereas Electrodynamics is the study of moving charge (current).
Lightning
Checkpoints Practise
Chapter 4
Questions 7
Questions 7