Electrostatic Machines
- Two kinds of electric energy : Static electricity and Current electricity.
- When an electrostatic force acts between charged particles , assign an electric potential energy, U. The difference in U of the system in two different states, initial i and final f, is
∆U = Uf – Ui
Reference point : Choose U = 0 at infinity. If the system is changed from initial state i to the final state f, the electrostatic force does work,
∆U = Uf – Ui = -W
Thus, potential energy is a scalar.
Work done by an electric field shown in Figure is given as
W = F . d and = q Ē
So W = qĒ . J = qEd cose
Where q is the angle between electric field and displacement
(1) Positive W→U decreases (2) Negative W→U increases
Electrostatic Machines : Basic Principle
- In electromagnetic machines, current carrying conductors are moved in a magnetic field, so that the mechanical energy is converted into electrical energy.
- In electrostatic machines, charged bodies are moved in an electric field against the electrostatic field in order that mechanical energy is converted into electrical energy.
- There are two types of electrostatic generators :
(a) Van de Graaff generator (b) Electrostatic generators