Draw a labelled diagram of Van de Graaff generator. State its working principle to show how introducing a small charged sphere into a larger sphere, a large amount of charge can be transferred to the outer sphere. State the use of this machine and also point out its limitations.
Draw a labelled diagram of Van de Graaff generator. State its working principle to show how introducing a small charged sphere into a larger sphere, a large amount of charge can be transferred to the outer sphere. State the use of this machine and also point out its limitations.
Van de Graaff generator is a device used for building up high potential difference of the order of a few million volts.
Principle : The working of Van de Graaff generator is based on the following two electrostatic phenomena.
(i) Discharging action at sharp points (corona discharge) i.e., electric discharge takes place in air or gases readily at the pointed ends of conductors.
(ii) If a charged conductor is brought into internal contact with a hollow conductor, all of its charge transfers to the hollow conductor, howsoever high the potential of the latter may be.
Construction : It is a big spherical conducting shell S kept over insulating pillars. A long narrow insulating belt is wound around two pulleys P1 andP2 and B1,B2 are two metal combs with sharp points. B1 is known as spray comb and B2 collecting comb.
Working : The spray comb provides positive potential by high tension source. The positive charge is sprayed on belt. As belt moves and touches the sphere, a negative charge is induced on the sharp ends of collecting comb B2 and similar positive charge is induced on the further end of B2. This positive charge moves immediately to the outer surface of S, because of discharging action of sharp points of B2, the positive charge on the belt is neutralized. The uncharged belt moves downwards and collects the positive charge from B1, which is then collected by B2. This process is repeated and the positive charge on S goes on accumulating. In this way, voltage differences of as much as 6 or 8 million volts (with respect to the ground) can be created.
Use : Van de Graaff generator is used to create high potential differences that are used to accelerate charged particles such as electrons, protons, ions, etc., used for nuclear breakdown.
Limitations :
1. It is a series of combination that allows only one way for moving charge.
2. It can accelerate only the charged particles and not the uncharged particles.
Van de Graaff generator is a device used for building up high potential difference of the order of a few million volts.
Principle : The working of Van de Graaff generator is based on the following two electrostatic phenomena.
(i) Discharging action at sharp points (corona discharge) i.e., electric discharge takes place in air or gases readily at the pointed ends of conductors.
(ii) If a charged conductor is brought into internal contact with a hollow conductor, all of its charge transfers to the hollow conductor, howsoever high the potential of the latter may be.
Construction : It is a big spherical conducting shell S kept over insulating pillars. A long narrow insulating belt is wound around two pulleys P1 andP2 and B1,B2 are two metal combs with sharp points. B1 is known as spray comb and B2 collecting comb.
Working : The spray comb provides positive potential by high tension source. The positive charge is sprayed on belt. As belt moves and touches the sphere, a negative charge is induced on the sharp ends of collecting comb B2 and similar positive charge is induced on the further end of B2. This positive charge moves immediately to the outer surface of S, because of discharging action of sharp points of B2, the positive charge on the belt is neutralized. The uncharged belt moves downwards and collects the positive charge from B1, which is then collected by B2. This process is repeated and the positive charge on S goes on accumulating. In this way, voltage differences of as much as 6 or 8 million volts (with respect to the ground) can be created.
Use : Van de Graaff generator is used to create high potential differences that are used to accelerate charged particles such as electrons, protons, ions, etc., used for nuclear breakdown.
Limitations :
1. It is a series of combination that allows only one way for moving charge.
2. It can accelerate only the charged particles and not the uncharged particles.
