Static Electricity

Question 1

SI unit of electric charge

Answer 1

Coulomb (C)

Question 2

What is the amount of charge carried by an electron

Answer 2

1.6 x 10^-19 C

Question 3

Electrical insulators and Electrical conductors: Motion of charged particles

Answer 3

Electrical insulators: Charged particles are not free to move about

Electrical conductors: Charged particles are free to move about

Question 4

Electrical insulators and Electrical conductors: Ability to conduct electricity

Answer 4

Electrical insulators: Low

Electrical conductors: High

Question 5

Electrical insulators and Electrical conductors: Method of charging

Answer 5

Electrical insulators: Friction (Rubbing)

Electrical conductors: Induction

Question 6

Electrical insulators and Electrical conductors: Examples

Answer 6

Electrical insulators: Glass, Perspex, Silk, Wool

Electrical conductors: Metals, Steel, Fluids with mobile charged particles

Question 7

Electrostatic charging by friction

Answer 7

When insulators are rubbed together, electrons move from one insulator to the other. The electrons moved remain at the surface where the rubbing was. Insulator that gained electrons become negatively charged while insulator that lost electrons become positively charged

Question 8

Charging conductors by induction

Answer 8

Induction is the charging of conductors without contact. Conductors cannot be charged by friction as mobile electrons can be easily transferred to and away from conductors

Question 9

Neutralising charged insulators

Answer 9

A charged object is neutralised by discharging the excess charges on it.

Insulators can be discharged through heating or by providing humid conditions

Conductors can be discharged by earthing

Question 10

What is electric force

Answer 10

An electric force is the attractive or repulsive force that electric charges exert on one another

Question 11

What is electric field

Answer 11

An electric field is a region in which an electric charge experiences an electric force

Question 12

Direction of electric field

Answer 12

The direction of an electric field is the direction of the force that would act on a small positive charge

Question 13

Strength of electric field

Answer 13

The strength of an electric field is indicated by how close the field lines are to one another

Question 14

Strength of electric field

Answer 14

The strength of an electric field is indicated by how close the field lines are to one another

Close together = Stronger
Further apart = Weaker

Question 15

Electric field lines of parallel plates

Answer 15

The electric field lines start from the positively charged plate and end at the negatively charged plate. The field is uniform near the middle of the plates

Question 16

Hazards of electrostatics: Lightning

Answer 16

-Thunderclouds are charged by friction between water molecules in the thunderclouds and air molecules in the atmosphere

-Negative charges accumulate at the bottom of the clouds

-These repel the electrons near the surface of the Earth, causing the surface of the Earth to be positively charged

-When the accumulation of charge is large, the air particles nearby are ionised

-The ionised air particles provide a conducting path for the electrons in the clouds to reach the Earth

-When the electrons travel down the conducting path to the Earth, lightning forms

Question 17

Why is lightning considered a hazard

Answer 17

Damage to buildings and cars, and harm people

Question 18

What safety measures are taken to prevent potential damage from lightning

Answer 18

-Lightning rod on buildings

-Lightning alert

-Closure of outdoor areas during thunderstorms

Question 19

Hazards of electrostatics: Electrostatic discharge

Answer 19

-Excessive charges may build up on objects due to friction

-Electronic equipment, such as computer boards and hard drives, can be easily damaged by electrostatic discharge

-Such equipment are usually packed in antistatic packaging

Question 20

Applications of electrostatics

Answer 20

-Photocopiers

-Spray painting

-Crop sprayers

-Electrostatic precipitators