Electricity is the presence or flow of charged particles. There are two types of electricity:
- Static electricity (presence)
- Current electricity (flow)
What is electric charge?
- Atoms are made up of charged subatomic particles such as electrons (negatively charged) and protons (positively charged). Neutrons have no charge (they are neutral)
- Electric charge is the property of a body that causes it to experience an attractive or repulsive force toward another body
- Because protons are stuck in the nuclei of the atoms, the net charge of a body is usually dependent on the excess of or lack of electrons (these can be removed from the surface of a material)
Static electricity
- This is the buildup of charge on an insulator
- An excess of electrons on a surface results in a net negative charge on the object
- A lack of electrons on a surface results in a net positive charge on the object
- Like charges ($+$ and $+$ OR $-$ and $-$) repel and unlike charges ($+$ and $-$) attract each other
The Principle of Conservation of Charge
- Charges are neither created nor destroyed
- Thus charges and their carriers such as electrons can only be transferred from one object to another
How do we charge objects?
This is also called electrification. Objects can be charged by:
- Friction
- Conduction
- Induction
- Polarization
Charging by friction
- This is the transfer of electrons from one object to another when the two objects are rubbed against each other
- One object loses electrons and in this way the object becomes positively charged
- The other object will thus become negatively charged because it now has an excess of electrons
- Some objects are better at picking up the electrons whereas others are better at losing electrons
- By the triboelectric effect: glass becomes positive when it is rubbed with silk (which will thus become negative)
Video on the Van de Graaff generator: