Electric Charge
An electron is the smallest known particle that can hold an electric charge
Electrons are part of an atom
Atoms cannot be seen without using a special instrument known as an electron microscope
At the center of an atom is the nucleus which is made up of positively charged protons and neutrons which have no charge
Electrons are negatively charged and orbit the nucleus
Elements such as Copper have 29 atoms, where Hydrogen has just one
Each element has different types of atoms; e.g., Copper atoms are different to those of Hydrogen
All materials can be classified as having the electrical properties of conductor, insulator or semiconductor
Copper is a good conductor that shows little resistance to electron flow
A voltage is always present between two points with a different number of electrons
Electron flow is greater in materials that that are good conductors.
Conductors, Insulators and Semiconductors
Conductors are mostly metals such as silver, gold, copper and aluminium
A conductor has less resistance to electron flow than insulators
Insulators are materials that prohibit the flow of electrons unless the voltage is high enough to break down the insulator and allow electron flow
Semiconductors are neither conductors or Semiconductors are treated with a chemical (doped) to give it special properties
Conductor
Insulator and Breakdown Voltage
Semiconductor
Gold
Mica - 2,000V
Silicon
Silver
Glass - 900V
Germanium
Copper
Paper - 500V
Carbon
Electric Current
Current is the flow of electrons from a point where there are more electrons to a point where there are less electrons
For current to flow a voltage must be present
Electron flow is from negative where there is an excess of electrons, to positive where there are less electrons
However electricians refer to current flow as positive to negative
This is called conventional current flow
Electric current is measured in Amps
The symbol for current is the letter A
In an electric circuit current does the work and voltage cause the current flow
Electromotive Force
The voltage from a voltage source such as a battery is also known as electromotive force or EMF
The symbol for EMF is the letter E
Voltage or EMF measured between two points is also known as electrical pressure
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