Charging

1) positive charges
2) negative charges

The process of providing an object with these charges is called charging.

It can be done in three different ways:

1) By rubbing the objects in question - two objects against each other
2) By bringing into contact - one with a charge with an uncharged one
3) By bringing one object closer to the other, but not touching

Electrostatic Induction

The process of providing an object with a charge, without touching it, is called electrostatic induction.

The metal sphere is mounted on an insulating stand. The sphere has a mixture of protons and electrons. When a charged object is brought closer, the charges in it rearrange themselves - like charges repel and unlike attract - on the sides of the sphere. Then the sphere is earthed and the free charges - not attracted to those of the external object - either move to the earth or get neutralized by electrons that come from the earth. Once the earth connection is removed, the sphere is positively or negatively charged - without being in contact with the charged external object. This is electrostatic induction.

Please answer the following questions.

1) Only metals can be charge by electrostatic induction. Explain.
2) Explain how you can charge a metal sphere positively by electrostatic induction.
3) Explain the phenomenon of lightning by electrostatic induction. Why is it dangerous to hold sharp meta objects while lightning?
4) In tropical countries, the tall coconut tree, that you often see along beaches, often becomes a victim to lightning. Explain.
5) You are not supposed to be under a tree while lightening. Explain the science behind it.
6) You see metal chains hanging down from the bodies of petrol tankers. Explain the significance of them.
7) You see metal spikes on the wings of an aircraft. What are they for?