Static Electricity

Question 1

Charges

Answer 1

Positive and negative charges are measured in coulomb.

Question 2

Laws of Electrostatic

Answer 2

Like electric charges attract, unlike electric charges repel.

Question 3

Electric field

Answer 3

A region of space in which an electric charge experiences an electric force.

Question 4

Electric Force

Answer 4

The attractive/repulsive force that electric charges exert on one another.

Question 5

Neutralising Charged Insulators

Answer 5

Insulators can be discharged through heating or by providing humid conditions

Question 6

Neutralising Charged Conductors

Answer 6

A charged conductor can be discharged by earthing because electrons are free to move about in conductors.

Question 7

Earthing

Answer 7

To provide a path for excess electrons to flow away (or to) an electrically charged conductor.

Question 8

Direction of electric field at a point

Answer 8

Direction of the force that would act on a small positive charge placed at that point in the field).

Question 9

HAZARDS OF ELECTROSTATICS

Answer 9

1. Lightning
   Flashes of lightning just before and during a thunderstorm are due to a large quantity of electric charge being built up in the heavy thunderclouds. The thunderclouds are charged by friction between the water molecules in the thunderclouds and the water molecules. When the charge on the thunderclouds is sufficiently large, it can ionise the air which then provides a conducting path for a large quantity of charge to be discharged to the nearest or sharpest object on the ground.

Solution:
Lightning conductor provides a steady discharge path for the large number of electrons in the air to flow from the top of the building to the earth. In this way, the chance of a lightning bolt (due to sudden discharge) is minimised.

2. Fire or an explosion due to excessive build-up of electric charges produced by friction

Solution:
In the case of the aircraft, the tyres are made
of slightly conductive rubber so that the large amount of
charge build-up on the body of the aircraft during flight
can be discharged harmlessly during touchdown.

3. Electrostatic discharge can also damage electronic equipment, such as circuit boards and hard drives.

Solution:
They are usually packed in antistatic packaging.
Antistatic materials have a thin layer of metallised film, which acts as an electrostatic shield for the equipment placed inside.

Question 10

Application of electrostatic

Answer 10

1. Photocopiers
2. Electrostatic precipitator
3. Spray painting
4. Van Der Graff generator