Topic 2: Electricity - Subtopic 3: Static Electricity

Question 1

What happens when two charged particles are close together?

Answer 1

• Exert a force on each other
  (Attractive or Repulsive)

Question 2

How do we know whether two objects attract or repel?

Answer 2

• Depends on charges
• Charges opposite, attract
• Charges same, repel

Question 3

What type of force is attraction and repulsion between two charged objects?

Answer 3

Non-contact force

Question 4

What is the difference between electricity and static electricity?

Answer 4

• Electricity is caused by the movement of charge in a circuit (occurs in conductors)
• Static Electricity is caused by a build up of stationary charge on a surface

Question 5

What are examples of static electricity?

Answer 5

• Accumulation of dust particles on surface
• Hair sticking up after combing with plastic comb
• Going down plastic slide
• Rubbing balloon and sticking to wall
• Sparking

Question 6

What does it mean when objects are electrically neutral?

Answer 6

The negative and positive charges are evenly distributed within the object

Question 7

What force is observed when two objects with different types of charge come together?

Answer 7

A force of attraction

Question 8

What force is observed when two objects with the same type of charge come together?

Answer 8

A force of repulsion

Question 9

What happens when you rub a balloon on a woolly jumper?

Answer 9

Electrons transfer onto the balloon by friction, making the balloon negatively charged and the jumper positively charged

Question 10

Why does a charged balloon stick to a wall?

Answer 10

The electrons on the balloon repel electrons on the wall’s surface, while positive charges on the wall are attracted to the negatively charged balloon

Question 11

What can the build-up of electrostatic charge lead to?

Answer 11

Sparking

Question 12

Give an example of sparking in everyday life

Answer 12

The small electric shock felt when touching a metal door handle, or when touching another person after walking on vinyl or nylon carpet

Question 13

When does a spark occur between two objects?

Answer 13

When there is a large potential difference between them, causing a current to flow

Question 14

What is an earthed conductor?

Answer 14

A wire, usually made from copper, that allows current to flow to the Earth

Question 15

Why does current flow through copper wire rather than through a person?

Answer 15

Because copper has a lower resistance than a person

Question 16

What happens when the potential difference between two objects becomes very large?

Answer 16

The electric field may become strong enough to cause the breakdown of air, allowing an electrical discharge (large spark) to travel through the air

Question 17

What are two dangers of sparking?

Answer 17

Electrocution (e.g. by lightning) and ignition of a fire or explosion

Question 18

How is lightning formed in a storm?

Answer 18

Ice crystals in clouds rub together, moving electrons between them. The top of the cloud becomes positively charged and the bottom negatively charged

Question 19

What is the approximate potential difference between a cloud and ground during lightning?

Answer 19

Around 1

Question 20

What causes lightning to strike?

Answer 20

The cloud discharges a large spark as negative charges jump to meet positive charges on the ground

Question 21

Why is static charge dangerous when refuelling aeroplanes?

Answer 21

Friction between fuel and pipe causes static charge build-up, which could create a spark that ignites the fuel and causes an explosion

Question 22

How can the risk of sparking be reduced when refuelling aircraft?

Answer 22

By connecting the fuel tank to the Earth with a bonding line, which carries excess charge to the ground

Question 23

What does a bonding line do?

Answer 23

It earths the aeroplane by carrying excess charge through to the Earth, removing the risk of sparks

Question 24

Why are electrons on the ground repelled when a storm cloud is nearby?

Answer 24

Because the bottom of the cloud is negatively charged and repels the electrons on the ground

Question 25

Between what two types of objects does sparking often occur?

Answer 25

Between a charged insulator and an earthed conductor

Question 26

What does a charged object create around itself?

Answer 26

- Electric Field

Question 27

How can electric fields be shown?

Answer 27

- Electric Field Line - Point away from positive charges - Point towards negative charge

Question 28

What is the strength of the electric field dependent on?

Answer 28

- Distance from the object creating field

Question 29

What is an electric field?

Answer 29

- Region where a charged object will experience an electric force

Question 30

What is a uniform electric field?

Answer 30

- Created between two parallel plates - Straight parallel lines from positive to negative