Electrostatics 2.0

Electrostatics 2.0

1. Quantisation of charge

   • The basic unit of charge, called the elementary charge,e, is the amount of charge carried by one electron.
   • The charge on a single electron is q = 1,6 x 10 C.
     • All other charges in the universe consist of an integer multiple of this charge - known as charge quantisation.
       • Q=nq
         • Q - Charge on the object
         • n - Is an integer multiple ( pos or neg)
         • q - Charge of an electron, 1,6 x 10
   • 1C charge is a very large charge. To obtain 1C charge, 6,25 x 10 electrons are needed. In electrostatics we then work in micro-coulombs (1 C= 1 x 10 C) and nanocoulombs (1nC = 1 x 10 ).
   • An electron is negatively charged, charge carried by the electron, q , is, -1,6 x 10 C
   • A proton is positively charged, charge carried by the proton, q , is, +1,6 x 10 C.

2. Polarisation

   • An object that is charged can attract an object that is uncharged.
     • How it works: When electrons are transferred onto an object due to friction it is negatively charged. eg: If a balloon is negatively charged due to friction and is brought closer to a wall that has no charge ( is neutral ) the opposite charges will repel leaving the positive charges which will be attracted to the negatively charged balloon. Polarisation has taken place.
   • Polarisation of insulators
     • Electrons bonded to the atom of an insulator cannot freely move through the substance. Polarization can take place on a neutral insulator caused by electrostatic power from a charged object.
     • Temporary dipoles are the north and south pole of a polarized object, eg: The wall that was polarized by the balloon.
     • Water has a permanent dipole. If the positively charged balloon is brought closer to the water, the molecules can rotate so that the negative sides all line up towards the rod. Stream of water will be attracted to the positively charged balloon. Opposite charges attract.