Static electricity

Question 1

State the laws of electrostatics (2)

Answer 1

1) Two like charges repel each other

2) Two unlike charges attract each other

Question 2

What happens when we earth a charged object?

Answer 2

Neutralisation process occurs. Electrons will move towards the charged object or towards the earth in order to neutralise the object.

Question 3

How do we charge a body?

Answer 3

1) By direct contact (only to charge conductors)
2) By friction (to charge non-conductors)
3) By electrostatic induction (to charge conductors)

Question 4

Describe the process of electrostatic induction

Answer 4

1) If we want to charge a conductor negatively, bring a positive metal rod near it.
2) Earth the metal sphere. The electrons will move up and neutralise the positive charges.
3) Remove the earth wire first.
4) Remove the metal rod. The negative charges are uniformly distributed

Question 5

What is charge measured in?

Answer 5

Coulombs

Question 6

Describe a conductor and give examples

Answer 6

A conductor is a body having large number of free electrons in its structure. It is more likely to give its outermost electrons. E.g. all metals, acids, grahite

Question 7

Describe an insulator and give examples

Answer 7

An insulator is a body having no free electrons in its structure. It is more likely to accept electrons. E.g. glass, silk, wood

Question 8

How are insulators charged by friction?

Answer 8

When an insulator is rubbed against another insulator there is a transfer of electrons from one body to another. If one gains electrons the other will lose electrons. One body becomes negatively charged and the other becomes positively charged

Question 9

Describe 2 experiments to demonstrate charging by friction

Answer 9

1) Bring the negatively charged object near neutral pieces of paper lying on a table. The paper jumps and sticks to the negatively charged object. This is due to attraction by the negative charges.
2) Bring the negatively charged object close to a fine stream of water flowing from a tap. The negatively charged object attracts the neutral stream of water

Question 10

What does the charging of solids involve?

Answer 10

The movement of elctrons

Question 11

Define an electric field

Answer 11

A region in which an electric charge experiences a force

Question 12

What are the directions of the electric field for negative and positive charges?

Answer 12

The are directed outwards for a positive charge and inwards for a negative charge

Question 13

How do electric lines of force emerge and move?

Answer 13

They always emerge at 90º and move from positive to negative charge