Working Principle of Van de Graff generator

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What is the working principle of Van de Graff generator?

 

Akash Rai asked.

 

Schematic view of a classical Van de Graaff-ge...

 

Answer: This is a question asked by many of the students.

 

There are basically two principles involved. The principle stresses in NCERT text book is that,

 

Photograph of a Van de Graaff generator.

Photograph of a Van de Graaff generator. (Photo credit: Wikipedia)

 

If we consider two concentric spheres connected electrically, then any charge given to the inner conductor will immediately be transferred to the outer sphere, irrespective of the amount of charge already present on the outer sphere. This happens because, the inner sphere is always at a higher potential and charges flow from high potential to low potential.

 

Another principle involved is the action of sharp points and corona discharge.

 

When a conductor with sharp points are charged, there will be greater surface charge density near the sharp points and the electric field near them will be high. This can ionise the surrounding air and can cause the charge to leak away. Thus a charged metal with sharp points will get discharged by this action.; the corona discharge.