By:Ch.anvesh

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ContentsIntroductionPrinciple of generatorStatic electricityTriboelectric seriesCharge developed on materialThe GeneratorConstructionCharge concentrationWorkingApplicationsLimitations

Introduction

Principle of Generator:

Generally generators works on the principle of faraday’s law. but, our Van De Graaff Generator works on the static electricity concept.

This generator doesn’t have field winding and conductor.

Static electricity:Static electricity is an imbalance

of electric charges within or on the

surface of a material. if you rub a

glass with a silk cloth, the glass

will develop a static charge that can attract small bits of papers.

The Nucleus:We know atom consists of nucleus.

Nucleus consists of equal number of neutron’s and proton’s which makes atom neutral.

This nucleus is surrounded by electrons which will rotate in orbit surrounding nucleus.

Triboelectric series:Some atoms hold on to their electron’s more tightly than others do.

How strongly matter holds on to it’s electron’s determines it’s place in the ‘Triboelectric series’.

Charge developed on material:

Charge developed depends on:

1. Amount of contact area

2. Humidity-measure of moisture in the air.

The Generator:The American physicist Robert.j.Van De Graaff invented the van de Graaff generator in 1931.

This is the device which can produce voltages as high as 1 million volts.

Construction of Generator:Major parts of Generator are:

Motor

Two rollers

A belt

Two brush assemblies

An output terminal(usually a aluminum sphere).

Charge concentration:Charge is much concentrated at roller than at belt, rollers electric field is much stronger than the belt’s at location of the lower roller.

The strong negative charge from the roller now begins to do two things:

It repels the electrons near the tips of the lower brush assembly.

It begins to strip nearby air molecules of their electrons.

Working of Generator:As already said it works based on static electricity principle.

The lower roller induces positive charge on belt and the belt transfers the charge to sphere.

Applications 1.It is used to generate x-rays, which is widely used in medicine field.

2.It is used in atom smasher’s, which is used in research purposes.

3.It found applications in physics, medicine, and astro physics.

Limitations •Its series connection allows only one route for the movement of charges.

•For generating high voltages, size becomes more and also cost becomes more.

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