Van de Graaff Generator is a device for producing a larger electrostatic potential difference of an order of 10^7 (V). The Van de Graaff Generator was invented by a Robert. J. Van de Graaff in 1929, so the device got the name Van de Graaff Generator.
Principle:
The basic principle behind the working of Van de Graaff generator was Electrostatic Induction and Action of points.
Construction:
- The top part of the Van de Graaff generator consists of a hollow metallic sphere which is mounted using the insulating pillars. The hollow metallic sphere is denoted by A.
- The top part of the Van de Graaff generator ( the metallic sphere) consists of a pulley B and the bottom part of the Van de Graaff generator consists of a pulley C.
- The middle part consists of insulating pillars, inside which the belt passes through the pulley.
- The belt is made up of a silky material which moves continuously over the pulley.
- The belt is made to rotate with the help of an electric motor which is connected to the pulley.
- Two combs (conducting materials) E and D which consists of needles are placed at the top and the bottom respectively.
- The Comb D is provided with an electric potential 10^4 V.
- The Comb E is placed inside the hollow metallic sphere.
Working:
- The High electric field near the Comb D, makes the air to ionize due to the action of points.
- The positive charges are repelled on towards the belt and the negative charges are attracted towards the Comb D.
- The repelled positive charges which are stick to the belt is taken up to the Comb E.
- Then the electrostatic Induction makes the Comb E to acquire a negative charge and the sphere acquires a positive charge.
- The outer side of the sphere consists of positive charges. (Acquired positive charges)
- The ionization of air takes place at the Comb E and the negative charges are neutralized by the acquired positive charges.
- The neutralization of charges takes place at the pulley (B) region and the belt moving towards the Pulley (C) won’t have any charges.
- The process will repeat ‘n’ number of cycles and at one stage, there won’t be any spaces for positive charges and the leakage of charges will occur on the machine.
- The limiting point is a term used to denote the peak point before starts to leakage.
- By using the gas-filled steel chamber at high pressure, the leakage of charges due to an air ionization can be reduced.
Advantages:
- We are giving the input in the order of 10^4 volt but we are getting 10^7 volt.
Disadvantages:
- Leakage of charges at the final stage of each and every cycle.
Applications:
- The high voltage produced from this Van de Graaff Generator can be used to accelerate protons and deuterons for the purpose of nuclear disintegration.
