• Not moving charges.
  • Material like amber, when rubbed, can move small objects
  • The technical term is that the ‘balloon’ or likewise, is electrically charged
  • There are two types of charge:
  • positive
  • & negative
  • if we are looking at atoms, protons are positively charged and electrons are negatively charged
  • An object that is not charged is referred to as neutral.
  • A neutron has no charges

  • In most situations we don’t look at atoms, we look at whole objects
  • If an object has more electrons that usual it will be negatively charged.
  • If it has less electrons, it will be positively charged.
  • In most cases we can use friction and rub electrons from one object to another to charge it.
  • It is important to note:
  • electrons do the moving, NOT protons
  • the charge doesn’t last long due to interactions with air
  • it is not restricted to solids

  • electrostatic precipitation – in chimneys.  Smoke and dust are ionized and stick to the metal plates in a chimney
  • the basic technique of charging small particles is how photocopiers work

Charging an object

  • can be easy or hard depending on the conductivity of the object.
  • In a conductor electrons can move very easily. E.g. metals have delocalized electrons that move easily.
  • In an insulator electrons are NOT free.
  • Things you can CHARGE are insulators.

Charging by induction ← induced charge

The charges are induced.

One is negative one is neutral.

This then induces a positive charge on one end of the neutral.

Attraction occurs.

Like charges repel, opposite charges attract

The gold leaf electroscope:

Join now!

Colomb’s Law

The force is dependant on:

  • Size of each charge
  • Square of the distance between them

where ε is the “permittivity of free space.”

Where: k = “coulomb constant”

        = 9 x 109 Nm2C-2

q1 + q2 are charges measured in coulomb’s.

Electric Fields:

  • We often draw field lines to visualize forces.  
  • You draw a field by pretending to put a ...

This is a preview of the whole essay