Topic 1 - Static and Current Electricity

Question 1

What is contained in the nucleus of an atom?

Answer 1

Protons and neutrons

Question 2

What is the overall charge of a nucleus?

Answer 2

Positive

Question 3

What gives an atom its overall size?

Answer 3

Electrons whizzing around the outside

Question 4

What is the relative mass of a proton?

Answer 4

1

Question 5

What is the relative charge of a proton?

Answer 5

+1

Question 6

What is the relative mass of a neutron?

Answer 6

1

Question 7

What is the relative charge of a neutron?

Answer 7

0

Question 8

What is the relative mass of an electron?

Answer 8

1/2000

Question 9

What is the relative charge of an electron?

Answer 9

-1

Question 10

What causes the build up of static electicity?

Answer 10

• When 2 insulating materials rubbed together, electrons are transferred from one to the other
• Positive static charge on one and negative charge on other
• Only electrons move, not protons
• Charges are equal + opposite

Question 11

What happens when a polythene rod and a cloth are rubbed together?

Answer 11

• Electrons move from the cloth to the rod

- Rod becomes negatively charged + cloth has equal positive charge

Question 12

What happens when an acetate rod and a cloth are rubbed together?

Answer 12

• Electrons transfer from the rod to cloth

- Cloth ahs negative charge + rod has equal positive charge

Question 13

What happens when two objects have the same charge?

Answer 13

• Repel from each other as same charges repel

- Electrostatic forces of attraction

Question 14

What happens when two objects the different charges?

Answer 14

• Attract together as opposite charges attract

- Electrostatic forces of attraction

Question 15

How does static electricity cause clothes to crackle?

Answer 15

• When synthetic clothes dragged over each other (e.g. in tumble drier), electrons transfer, leaving static charges on both
• Attraction between items + little spark as charges rearrange themselves

Question 16

How does static electricity cause car shocks?

Answer 16

• Static charge builds up between clothes + synthetic car seat; friction causes electrons to transfer
• When get out of car + touch metal door, charge flows giving a shock
• Some cars have conducting strips that hang behind car giving a safe discharge to earth

Question 17

How does static electricity cause shocks from door handles?

Answer 17

• Walk on nylon carpet wearing shoes w/ insulating soles
• Electrons transfer from carpet to you so charge build up on body
• If touch metal door handle, charge flows to conductor giving a shock

Question 18

How can a balloon be made to stick to a wall?

Answer 18

• Rub balloon against hair/clothes, so electrons transfer to balloon (giving it a negative charge)
• Sticks to wall although wall isn’t charged
• Charge on surface of wall moves a bit: negative charge repels so positive charge is on wall surface, attracting balloon, holding balloon to wall
• This is called induction

Question 19

How can a comb be charged to pick up small pieces of paper?

Answer 19

• Run comb through hair, so electrons transfer to comb so it’s negatively charged
• Picks up paper although paper has no charge
• Negative repels so positive on top sticking to comb
• Induction

Question 20

What causes lightning?

Answer 20

• Static charge
• Rain drops + ice rub together inside storm clouds
• Electrons transfer
• Positive charged on top and negatively charged on bottom
• Creates a voltage + spark as wants to get earthed

Question 21

How do paint sprayers use electrostatic charges to get an even coat on bikes and cars?

Answer 21

• Spray gun charged, charging small drops of paint
• Drops repel others as same charge, so get fine spray
• Object given opposite charge to gun, attracting fine spray of paint
• Method gives even coat + hardly any paint wasted
• Parts facing away from the gun still get painted; no shadows
• Same as how insecticides sprayers work

Question 22

How are electrostatic charges problematic when fuel filling and how can this be resolved?

Answer 22

• As fuel flows out filler pipe, static builds up
• Can easily lead to spark which can cause explosion
• Sparks prevented by being earthed

Question 23

How does earthing stop electrostatic charges building up?

Answer 23

• Dangerous sparks can be prevented by connected charged object to ground by conductor (earthing)
• Provides easy route for static charges to travel into ground so no charge can build up to shock or spark
• Electrons flow down conductor to ground if charge negative + flow up conductor from ground if charge positive

Question 24

Why must fuel tankers be earthed?

Answer 24

To prevent any sparks that might cause the fuel to explode

Question 25

What is current?

Answer 25

Rate of flow of charge around a circuit

Question 26

In the metal wires of a circuit, what is charge carried by?

Answer 26

Electrons

Question 27

Why are metals good conductors?

Answer 27

Have free electrons that are free to move

Question 28

What causes charge to build up?

Answer 28

When current flows past a point in a circuit for a certain length of time

Question 29

What is the formula for charge?

Answer 29

Charge = current x time

Q=It

Question 30

What is charge measured in?

Answer 30

Coulombs

Question 31

What is current measured in?

Answer 31

Amperes

Question 32

How does a bigger current affect the charge?

Answer 32

More charge

Question 33

What type of current do cells and batteries provide?

Answer 33

Direct current (d.c.)

Question 34

What is direct current?

Answer 34

Current that keep flowing in the same direction

Question 35

What does a direct current look like on an oscilloscope?

Answer 35

Always has same voltage so is just a straight line

Question 36

What type of current is mains electricity?

Answer 36

Alternating current - constantly changing direction