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# Tag Archives: North Carolina

## Working Principle of Van de Graff generator

What is the working principle of Van de Graff generator?

Akash Rai asked.

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,

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.

## A problem from Gravitation

Three identical bodies each of mass m are located at the vertices of an equilateral triangle with side r. At what speed they move if they all revolve under the influence of one another’s gravitation in a circular orbit circumscribing the triangle while still preserving the equilateral triangle

Asked Nitin gupta (from our mobile website http://m.askphysics.com)

Please post your answer now!

## The total force on charge q on the vertex

Can you please answer the following question?

Consider the charges q,q and -q placed at the vertices of an equilateral triangle. What is the force on each charge?

I actually didn’t understand the total force on charge -q at the vertex C of the equilateral triangle. How is it equal to root3Fn where n is the unit vector along the direction bisecting the angle BCA (Why?).

Thejaswini posted the question

Answer.