Vaan de Graaf Generator

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    Van De Graaff GeneratorPRINCIPLE

    THEORY

    CONSTRUCTION

    WORKING

    &APPLICATIONS

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    The device has the ability to produce

    extremely high voltages-as high as 20

    million volts

    The generator is to supply the high

    energy needed for early particle

    accelerators

    These accelerators are known as

    atom smashers .

    The resulting collision created

    other sub atomic particles and highenergy radiations such as X-rays.

    The ability to create these high energy collisions is

    the foundation of particle and nuclear physics.

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    Principle

    Working of the generator is based on twoprinciples:

    I. Discharging action of sharp points i.e., electric

    discharge takes place in air or gases readily at pointed

    conductors.

    II. If the charged conductor is brought in to internalcontact with a hollow conductor, all of its charge

    transfers to the surface of the hollow conductor no

    matter how high the potential of the latter may be.

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    Theory behind construction:

    If we have a large conducting spherical shell ofradius R on which we place a charge Q, it spreadsitself uniformly all over the sphere. The field outsidethe sphere is just that of a point charge Q at the

    centre; while the field inside the sphere vanishes.

    So the potential outside is that of point charge andinside it is constant.

    The potential inside the conducting sphere =

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    Now suppose that we introduce a small sphere of

    radius r, carrying a charge q, into the large one and

    place it at the centre. The potential due to this newcharge has following values.

    Potential due to small sphere of radius r carrying

    charge

    at the surface of small sphere

    at the large shell of radius R

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    Taking both charges q and Q in to account we have

    for the total potential V and the potential differencegiven by

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    Construction

    Details

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    ightening / sparking produced in

    Van De Graaff Generator

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    Demonstration of

    Van De Graff Generator

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    Sparks up to 35 cm in Length

    A Large Sphere Creates Higher Voltage

    A Large Size Ideal for Demonstrations

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    This science-show Van

    de Graaff Generator can

    deliver a spark over 48"

    long. The generator is 10'

    tall and has a 42"

    diameter collector.

    The author constructed

    the machine in 1988 for

    The Science Place

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    The High Voltage Van de Graaff

    Generator features a 25 cm

    diameter sphere which can

    generate approximately 400,000

    Volts.

    The size of the sphere, therounded edges of the sphere and

    the height of the sphere from the

    demonstration table contribute to

    the high voltages generated.

    Its large size, long sparks and

    high voltages make it ideal for use

    in larger rooms or lecture halls.

    An extra belt is included.

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    Fig - A horizontal Van de

    Graaff generator

    constructed for a company

    investigating effects of static

    electricity on aircraft

    components.

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