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Physics P2 Flashcards

1
Q

Structure of the atom

A

Nucleus in the middle- contains protons and neutrons, positive charge

Electrons whizz round nucleus with a negative charge

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2
Q

Proton

A

Mass- 1

Charge- positive

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3
Q

Neutron

A

Mass- 1

Charge- 0

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4
Q

Electron

A

Mass- 1/2000

Charge- Negative

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5
Q

How is the build up of static caused?

A

When two insulating materials are rubbed together, electrons will be scraped off one and dumped on the other
This will leave a positive charge on one and a negative charge on the other
Only electrons can move not protons, the way they transfer depends on the materials involved

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6
Q

When polythene rods are rubbed with a cloth duster what happens?

A

Electrons move from the duster to the rod. The rod becomes negatively charged and the duster is left with an equal positive charge

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7
Q

When an acetate rod is rubbed with a cloth what happens?

A

Electrons move from the rod to the cloth. The duster becomes negatively charged and the rod is left with an equal positive charge.

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8
Q

Like charges repel…

A

Unlike charges attract

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9
Q

Examples of static electricity sparks

A
  1. Clothing crackles
  2. Car shocks
  3. Shocks from door handles
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10
Q

Clothing crackles

A

When synthetic clothes are dragged over each other, electrons get scraped off. This leads to attraction and little sparks as the charges rearrange themselves

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11
Q

Car shocks

A

Static charge can also build up between your clothes and a synthetic car seat. Some cars have conducting strips which hang down behind the car, giving a safe discharge to earth

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12
Q

Shocks from door handles

A

If you walk on a nylon carpet wearing shoes with insulating soles, there will be a transfer of electrons from the carpet to you and and charge will build up on your body. Then if u touch a metal door handle the charge flows to the conductor and you get a shock

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13
Q

Give examples of electrically charged objects attracting other objects

A
  • Balloons can stick to walls

- A charged comb can pick up small pieces of paper

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14
Q

Balloons sticking to walls

A

Rubbing a balloon against your hair or clothes causes electrons to be transferred to the balloon, leaving it with a negative charge. If you hold it up to a wall it will stick even if the wall isn’t charged. That’s because the charges on the surface of the wall move- the negative charges on the balloon repel the negative charges on the wall, leaving positive charges on the surface of the wall.

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15
Q

What is induction?

A

The method of using a charged object to force charges in an uncharged object to move

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16
Q

A charged comb picking up pieces of paper

A

If you run the comb through your hair, electrons will be transferred to the comb and it will become negatively charged. It can then be used to pick up little bits of paper even though they have no charge, the comb near the paper causes induction

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17
Q

How is lightning caused?

A

Rain drops and ice bump together inside storm clouds knocking off electrons and leaving the top of the cloud positively charged and the bottom of the cloud negative. This creates a huge voltage and a big spark

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18
Q

Uses of static electricity

A

-Paint sprayers use electrostatic charges to get an even coat

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19
Q

Dangers of static electricity

A

Can cause problems filling fuel

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20
Q

Earthing

A

Dangerous sparks can be prevented by connecting a charged object to the ground using a conductor. Earthing provides an easy route for static charges to travel to the ground. This means no charge and build up and create a shock or spark.

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21
Q

Electrons flow down the conductor to the ground if….

A

…the charge is negative

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22
Q

The electrons flow up the conductor from the ground if…

A

…the charge is positive

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23
Q

How do paint sprayers work?

A

The spray gun is charged, which charges up the small drops of paint. Each paint drop repels all the others since they all have the same charge so you get a very fine spray. The object being painted has an opposite charge to the gun so attracts the fine spray. There are no paint shadows

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24
Q

Electrostatic charges and fuel filling

A

As fuel flows out of the filler pipe, static can build up. This can easily lead to a spark which may cause an explosion in dusty or fumey places like when filling up a car with fuel. This can be fixed with earthing

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25
Current
Rate of flow of charge around a circuit
26
What is current carried by?
Electrons
27
Why are metals good conductors?
They have free electrons which are able to move
28
Charge formula
Current x time
29
When a bigger current flows...
More charge passes round the circuit
30
What current to cells and batteries supply?
Direct current
31
What is direct current?
Current that keeps flowing in the same direction A direct current source is always at the same voltage so you get a straight line
32
How does charge move in a direct current
In one direction only
33
Voltage (potential difference)
Voltage is the driving force that pushes the current round. Kind of like "electrical pressure"
34
Resistance
Anything in the circuit which slows the flow down (ohms) The voltage is trying to push the current round the circuit and the resistance is opposing it
35
Increase the voltage...
...increase the current
36
Increase the resistance...
...then less current will flow
37
When an electrical charge goes through a change in voltage what happens?
Energy is transferred
38
Potential difference is the energy transferred per unit charge passed
Energy is supplied to the charge at the power source to 'raise' it through the voltage The charge gives up this energy when it 'falls' through any voltage drop in components elsewhere in the circuit.
39
The bigger the change in voltage...
...the more energy is transferred for a given amount of charge passing through a circuit
40
A battery with a bigger voltage will supply more energy to the circuit for every coulomb of charge which flows round it. Why is this?
The charged is raised up "higher" at the start and more energy will be dissipated in the circuit too
41
What happens to current at a junction?
Current is conserved, this means the total current entering a junction is equal to the total current leaving a junction
42
Ammeter
Measures the current flowing through the component | Must be placed in series (connected in a line with the component)
43
Voltmeter
Measures the voltage (potential difference) across the component Must be placed in parallel around the component under test- not around the variable resister or the cell
44
Static electricity
Charges are not free to move | This causes them to build up in one place and it often ends with a spark or shock when they finally do move
45
Fixed resister V-I graph
The current through a resistor (at constant temperature) is proportional to voltage. Different resistors have different resistances hence the different slopes
46
Filament lamp V-I graph
As the temperature of the filament increases, the resistance increases, hence the curve.
47
Diode V-I graph
Current will only flow through a diode in one direction as shown.
48
Light dependent resistor and resistance
1) In bright light, the resistance falls | 2) In darkness, the resistance is highest
49
Light dependant resistor
In bright light the resistance falls | In darkness the resistance is highest
50
Thermistor
In hot conditions the resistance drops | In cool conditions the resistance goes up
51
Why do resistors get hot when a current passes through?
Electrons collide with ions in the lattice that makes up the resistor This gives the ions energy which is emitted as heat
52
Electrical power
The rate in which an appliance transfers energy
53
When are all forces in balance?
When an object is stationary | When there's a steady velocity any direction
54
When are there unbalanced forces on an object?
When there is acceleration
55
Why do falling objects in a vacuum accelerate at the same rate?
Because there is no air resistance to slow the falling objects down
56
Newtons 3rd law
For every action there is an equal and opposite reaction
57
Newton's 1st law
If there are no forces on an object, or all the forces are balanced, the object will remain at rest or carry on moving at a constant velocity
58
Newtons 2nd law
If the forces acting on an object are unbalanced it will either accelerate or decelerate
59
Things that affect thinking distance
Reaction time | How fast you're going
60
What affects braking distance
How fast you're going The mass of the vehicle How good your brakes are How good the grip is
61
Thinking distance
The distance the car travels in the time between the driver noticing the hazard and applying the brakes
62
Braking distance
The distance the car travels during its deceleration whilst the brakes are being applied
63
How are cars designed to reduce momentum change?
Crumple zones Seat belts Air bags
64
How is ionisation caused by the 3 types of radiation?
Alpha pulls electrons out of orbit because it's positive Beta pushes electrons out of orbit because it's negative Gamma transfers enough energy to the electrons to break free from the atom
65
Alpha
``` Helium nuclei- 2 protons 2 neutrons Big, heavy, slow moving Strong positive charge Strongly ionising Stopped by paper ```
66
Beta
``` Electrons Fast and small Negative charge Moderately ionising Stopped by aluminium When one is released a neutron turns into a proton in the nucleus ```
67
Gamma rays
Weakly ionising | Stopped by thick lead
68
Nuclear fission
Slow moving neutron is fired at an isotope of uranium The neutron is absorbed making it unstable and causing it to split When it splits it forms two lighter elements, 2 or 3 neutrons and thermal energy
69
How is nuclear fission controlled?
Uranium fuel rods placed in a moderator to slow down the fast moving neutrons Control rods made of boron are raised and lowered between the fuel rods to limit the rate of fission by absorbing excess neutrons
70
Nuclear fusion
Two light nuclei (hydrogen) collide at high speed and fuse to create a larger nucleus (helium) and energy
71
Nuclear fusion advantages and disadvantages
- Releases a lot of energy- more than fission - Doesn't leave behind a lot of radioactive waste - Plenty of hydrogen for fuel - Requires high pressures and temperatures due to electrostatic repulsion of protons - Fusion reactors really expensive and hard to build
72
Cold fusion
- Scientists Stanley pons and Martin Fleischmann reported cold fusion - Many tried to repeat their work but few could do it reliably - Many people discredited it
73
Where does background radiation come from
- Naturally occurring unstable isotopes - Space - Human activity
74
Uses of alpha
Fire alarms A weak alpha source is placed close to two electrodes, the source causes ionisation and a current flows Smoke will absorb the radiation so the current stops and the alarm sounds
75
Uses of gamma rays
Sterilising food and medical equipment Doesn't involve high temperatures Treat cancer Tracers
76
Uses of beta
Tracers | Thickness gauges
77
Dangers of radioactivity
Ionising Can cause cancer Radiation sickness
78
How to protect yourself from radioactivity
Use tongs Arms length Pointing it away and avoid looking directly at it Keep it in a labelled lead box
79
How do protect yourself by working with nuclear radiation
- Wear full protective suits - Lead lined suits/ lead barriers - Remote controlled robot arms
80
Nuclear power advantages
- Releases a lot of energy - Pretty safe - Very reliable - Doesn't release CO2 or sulphur dioxide - Fuel is cheap and readily available
81
Nuclear power disadvantages
- Reactive waste products - Public perception is negative - Danger of polluting land and rivers - Carries the risk of leaks or major catastrophes - Cost is high
82
Nuclear waste
- Cannot be recycled - Long half lives - Dangerous - Can be dealt with using vitrification - Packing into thick metal containers and burying the waste into a deep hole and filling it with concrete
83
Vitrification
Melting nuclear waste with other materials to form a type of glass The liquid glass is sealed inside steel canisters and buried deep under ground

Science (4 decks)

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