Question

1. Identify the device

• Moving coil Galvanometer
• Cyclotron
• Photovoltaic cell
• Van de Graft electrostatic generator

2. Explain the construction and working of the above device

3. What happens if the upper metal sphere is replaced by a cubical shaped metal? Explain.

Answer 1

1. Vandegraff generator 

2. Van de graff generator:

Van de Graff generator is used to produce very high voltage.

Principle:

If two charged concentric hollow spheres are brought in to contact, charge will always ow from inner sphere to the outer sphere.

Construction and working:

The vande Graff generator consists of a large spherical metal shell, placed on an insulating stand.

Let p₁ and p₂ be two pulleys. Pulley p₁ is at the center of the spherical shell S. A belt is wound around two pulleys p₁ and p₂ .

This belt is rotated by a motor. Positive charges are sprayed by belt. Brush B₂ transfer these charges to the spherical shell. This process is continued. Hence a very high voltage is produced on the sphere.

3. The charge density on the pointed edge is higher than at surface. Hence charge will leak from the cubical shaped metal.