Chapter - 17 (Static electricity)

Question 1

What are the 2 types of charges?

Answer 1

• Positive
• Negative

Question 2

what happens to opposite charges?

Answer 2

attract

Question 3

What happens to like charges?

Answer 3

Repel

Question 4

What is electric charge measured in?

Answer 4

Coulombs (C)

Question 5

How is electrostatic repulsion caused?

Answer 5

When the charges are the same as reach other (repulsion)

Question 6

How do insulating solids get a charge?

Answer 6

• by friction to transfer electrons
• by removing electrons that have a negative charge are left with a positive charge

Question 7

What is the process for producing an electrostatic charge?

Answer 7

1. Suspend insulating material using a cradle and a length of string so that the material can rotate softly
2. Rub one end of material using a cloth (in order to give it a charge)
3. Take a 2nd piece of insulating material and charge that by rubbing with a cloth
4. Hold the charged end of the 2nd piece end of First piece

• if the material piece rotates away (repelled) then materials have the same charge
• if the First piece move towards (is attracted) then they have opposite charges

Question 8

What does a charged object create?

Answer 8

Electric field

Question 9

How is electric field shown?

Answer 9

Field lines point away from positive charges towards negative charges

Question 10

What does the direction of force refer to?

Answer 10

A positive charge, it is always electrons that are free to move according to that force.

Question 11

What does the strength of an electric field depend on?

Answer 11

Distance from the object creating the field.

• field is strongest close to the object (lines are close)
• field is weaker away from the charged object (lines are further away)

Question 12

What do objects in electric field experience?

Answer 12

Electric field

Question 13

What do the direction of the force depend on?

Answer 13

Charges are same or opposite

Question 14

What 2 options can the force be?

Answer 14

1. Attractive
2. repulsive

Question 15

What happens to the forces if charges are the same?

Answer 15

• (negative and negative) or (positive and positive)
• repulsive
• 2nd object will move away from the charge creating field

Question 16

What happens if the charges are opposite?

Answer 16

• (negative and positive)
• Attractive
• object move towards charge creating field

Question 17

What does the size of force depend om?

Answer 17

Strength of field at that point

Question 18

What does it mean when the force becomes stronger?

Answer 18

The distance between two charged objects decreases

Question 19

What does it mean when the force becomes weaker?

Answer 19

distance between 2 charged objects increases

Question 20

What should we note about the field lines?

Answer 20

Go from positive to negative

Same direction as the direction of the force on a positively charged particle at a point.

Question 21

What is the electric field between two parallel plates?

Answer 21

uniform electric field.

Question 22

What are the properties of electric field lines?

Answer 22

• directed from positive to negatuve plate
• parallel
• straight lines

Question 23

How are field lines around a charged conducting sphere?

Answer 23

• Symmetrical
• they repel (charge same)
• charges on surface will be evenly spread
• surface is conducting allowing them to move

Question 24

How can the field line be demonstrated?

Answer 24

Van der Graff Generator

Question 25

How can the field lines be demonstrated in schools?

Answer 25

- small pieces of paper - polystyrene beads - aluminum foil containers

Question 26

What is main difference in conductors and insulators?

Answer 26

Conductors - allow charge carrier to move freely Insulator - do not allow charge carriers to move Due to their internal structures.

Question 27

Define conductor

Answer 27

A material that allows charge (usually electrons to flow through it)

Question 28

What are examples of conductors

Answer 28

Silver Copper aluminum Steel

Question 29

What are the conductors made up of?

Answer 29

Positively charged metal ions with their outermost electrons delocalized.

Question 30

Why do metals conduct electricity?

Answer 30

- current is the rate of flow of charged particles - more easily the electrons are able to flow, the better the conductor.

Question 31

Define insulator.

Answer 31

Insulator is a material that has no free charges and does not allow the flow of charges.

Question 32

What are examples of insulators?

Answer 32

- Rubber - plastic - glass - wood

Question 33

What can be used to investigate electrical conductors and insulators?

Answer 33

Gold leaf electroscope (GLE)

Question 34

What does the GLE consist of?

Answer 34

- metal plate attached to one end of metal rod - other end is a thin leaf of gold foil - rod held by insulating collar inside a box with glass sides, allowing gold leaf to be seen and protected from draughts

Question 35

What happens when the GLE is charged?

Answer 35

- plate, rod, and gold leaf have same charge - they repel and leaf sticks out the side - when rod and leaf are discharged, (are neutral) the Leafs hang down.

Question 36

How do we test the electrical conductors and insulators?

Answer 36

- charge the plate of GLE so that gold leaf stands clear of the rod - carefully touch the plate of GLE with items being tested

Question 37

What should you do after you test for electrical conductors and insulators?

Answer 37

Record the observation: 1. Leaf falls: Material is a good conductor 2. Leaf remains in place: Object is poor conductor (good insulator) 3. Leaf falls slowly: Material is a poor conductor.

Question 38

What is an alternate way to test for electrical conductors and insulators?

Answer 38

An electronic charge detector