- Hey guys, here is a summary
video that you're gonna need
for your first AQA Physics exam
covering the first few topics.
Now this is just a quick
summary of everything.
If you want a checklist
to make sure you've covered everything,
loads and loads of quickfire question,
all those important,
important equations and units
that you have to learn,
then you can get that
over in the free revision
guide from website,
or you can get that from Amazon.
("Something Elated" by Broke for Free)
The different types of
energy can be remembered
by using Geeks Lunch.
I would admit, the U
doesn't stand for anything.
Gravitational potential energy.
Electrical energy.
Elastic potential energy.
Kinetic energy.
Sound energy.
Light energy.
Nuclear energy.
Chemical energy, as in batteries or food.
And heat or thermal energy.
You'll notice most of these involve
more than one type of energy.
For example, in the phone,
we have electrical energy going in
but we have chemical energy being stored
and then heat energy
'cause your phone gets hot,
light and sounds energy coming out.
With the match, we have
chemical energy being stored
and then kinetic energy being
used to strike the match
and then heat, light and a bit
of sound energy coming out.
With the fireworks, it was
stored as chemical energy
and then we are going
to have it transferred
into kinetic energy as it moves up.
As it explodes, we're going to have light,
heat and sound energy coming out,
and then gravitational potential energy
as it starts to fall,
kinetic energy as it falls back down.
The Law of Conservation of Energy tell us
that energy cannot be
created or destroyed.
It is only transformed into
another type of energy,
which is really cool because
it tells us that the energy
you're gonna have for
lunch or breakfast today
has been around since the
start of the universe.
The energy that's hovering
around your computer, your phone,
your lights has been around
since the start of the universe.
And the energy that you're
using, the kinetic energy,
the chemical energy that
you were using today
to get out of bed, do your daily things,
is going to be around until
the end of the universe.
Kinetic energy is equal to half times mass
times velocity squared.
Kinetic energy is measured in
joules, half is just a number,
mass is measured in kilograms
and velocity is meters per second.
And with this, remember,
it's just the velocity
that's squared, not the whole thing.
Elastic potential energy is equal to half
times the spring constant,
times extension squared.
Elastic potential energy
is measured in joules,
half is just a number,
extension is measured in meters,
and the spring constant is
measured in newtons per meter.
Gravitational potential
energy is equal to mass
times gravity times height.
Gravitational potential
energy is measured in joules,
mass in measured in kilograms,
gravitational field strength
is 9.8 newtons per kilogram,
and height is measured in meters.
I don't want to overload
you with too much math
but there is a bit more coming
so just take a tiny little break.
Change in thermal energy
is equal to mass times
the specific heat capacity
times change in temperature.
Change in energy is measured in joules,
mass is measured in kilograms,
specific heat capacity is
measured in joules per kilograms
brace degrees C, and change in temperature
is measured in degrees C.
Power equals energy transferred over time.
The units for power are
watts with a capital W,
energy transferred is
joules with a capital J,
and time is seconds with a small S.
Power is equal to work done over time.
Power is measured in watts,
work done is measured in joules,
time is measured in seconds.
While energy cannot be
created or destroyed,
it can be wasted.
Wasted energy is any energy
that comes out of a situation
that we didn't intend for it to be there.
For example, in a light bulb
we have electrical energy
going in, this is converted
into light, heat and sound.
The light is the useful
energy, whereas the heat
and the sound are not useful
energy, they are wasted energy.
And a worthy example
we'd love to describe is,
if we can say is that the
wasted energy dissipates
into the surroundings.
It spreads out so much, it
can't be collected and used.
It's not gone, it's still
there, it's just spread out.
It's dissipated.
Heat comes off and we can detect that
with an infrared camera.
We can see how well
the house is insulated.
The blue parts, the roof
are very, very cold,
so not much heat is escaping,
whereas the walls here and here
are very, very hot, so
lots of heat is escaping.
We can see that the roof is
blue and the windows are blue
suggesting that very good insulation.
New houses are built very
energy efficient and old houses
can be adapted to be
very energy efficient,
so we can have cavity wall insulation.
Double glazing.
Loft insulation.
Carpets.
Curtains.
Draft excluders.
If they still have them,
they can have a jacket
around the hot water tank.
Efficiency is equal to useful energy out
over total energy in,
and this can be expressed
as percentage or decimal.
Efficiency is equal to useful power out
over total power in, and
this can be a percentage
or a decimal.
When we think about
generating electricity,
we can either do that
with a renewable source
or with a finite source.
A renewable source is one
that isn't going to run out
and we can get more of it,
whereas a finite source
is going to run out.
Renewable sources include
things like the sun,
the wind, water, including tidal power,
hydroelectric power, wave
power, geothermal power,
whereas the finite resource
is going to be a fossil fuel,
so coal, oil, gas, or nuclear power.
The advantage of solar
power, the advantage
of the majority of renewable resources
is that they don't release carbon dioxide.
We're never going to run out of them,
and they're generally non-polluting.
The disadvantage of solar
is that it doesn't happen
during night and isn't
very good on cloudy days
or wintry days.
It can also be expensive to install.
Wind turbines, a
disadvantage of wind turbines
is that some people don't like them.
They also don't work very
well on non-windy days.
Tidal and wave power can be disruptive
to the local environment,
whereas the hydroelectric dam
involves flooding a large area,
which may include people's
homes or animals' habitats.
And the disadvantage to geothermal power
is that it can only be
used in volcanic countries.
The advantage of using
fossil fuels or nuclear power
is that they are very,
very readily available,
it's a very, very cheap
source of electricity,
and things like coal power stations
have a very short staff out time.
The disadvantage of
using coal, oil, and gas
is that they take millions
and millions of years
to create so we are
about to run out of them.
They are very, very heavily polluting,
so they release large
amounts of carbon dioxide
and other pollutants into the atmosphere,
which contribute to climate change.
The disadvantage of nuclear power
is that you have to store their nuclear,
radioactive waste for
long periods of time,
and there is a very small,
but there is a potential
risk of explosion.
You need to know all of
these circuit symbols.
I've made you handy flashcards for this,
but here is a quick recap.
This is a cell.
This is a battery.
You will notice that a battery
is more than one cell put together.
Here we have an ammeter.
Voltmeter.
A lamp or a bulb.
Diode.
And LED, light-emitting diode, resistor.
Variable resistor.
Fuse, thermistor.
LDR, light-dependent resistor.
Closed switch.
Open switch.
Here we have a circuit in series
where you can run your
finger the whole way through
from the batteries to all components.
And here we have a series in parallel
where it has branches or ladders.
You can't run your
finger around everything
without going over something twice.
You'll notice here we have an ammeter.
That is in series and our voltmeter,
that has to be in parallel
around the component.
Charge is a value of electricity
flowing through circuits.
Current is a flow of electrons.
Potential difference is what
pushes the current around.
And resistance is anything
that slows down the current.
Charge equals current times time.
Charge is measured in coulombs.
Current is measures in amps.
Time is measured in seconds.
Potential difference equals
current times resistance.
Potential difference is measured in volts.
Current is measured in amps.
Resistance is measured in ohms.
There are three current-potential
difference graphs
you're expected to recognize and draw.
Remember, current here
is measured in amps,
and potential difference
is measured in volts.
A resistor at a constant temperature,
the current and potential difference
are directly proportional to each other.
For a filament bulb, you have our graph
going through zero, looking like this.
This is what's, as the
temperature increases,
the resistance increases, and a diode
will only let current
flow in one direction,
so the graph looks like this.
The direction that it is pointing.
A thermistor is used in stuff
like your central heating,
and it's only gonna let current flow
at certain temperatures.
For example, at a high temperature,
our graph looks like this,
whereas at a low temperature,
the graph is going to look much lower.
So as the temperature changes,
the resistance changes.
For a light-dependent resistor,
whether the lights are on or off
is going to depend on
the quantity of light.
We can use this in street
lights or security lighting.
If we have a bright light,
that's what our graph
is going to look like, but
then if the light dims,
it is going to change.
So that resistance flowing
through the circuit
changes with the amount of light.
We can think of current as
electrons moving around a circuit
and in a series circuit, they
all move in the same way.
They all move with the same path.
So wherever we look in a series circuit,
the current is going to be the same.
However, in a parallel circuit,
the current comes out
of actually, all of this
is gonna pass the first ammeter,
move down here, and then
when it gets to this point,
it has two choices of where to go.
In go this way, pass this ammeter,
or down here, and this
may pass this ammeter.
So the current gets split.
Potential difference,
measured by a voltmeter.
Gonna mention the voltmeter
around the battery,
then a voltmeter around each of the bulbs,
and you'll notice that
the potential difference,
the voltage at the battery is
split across the components,
whereas in a parallel circuit,
the potential difference
that we have here across the battery
is the same as we have
across each of the branches.
Our circuits are getting
quite complicated now,
and we're going to be
looking at resistance.
When we have resistors
that are in a series,
the total resistance is
just them added together.
Whereas when we have resistance
that are in parallel,
the total resistance
is one over resistance,
so resistor one plus one over resistance,
and then resistor number two and so on,
so, current in a series circuit
is going to be the same
wherever you look at it,
but you have to add up
different potential differences
to get the total potential difference,
and add up the different resistances
to get the total resistance.
On a parallel circuit,
the current on each branch
is going to be equal to the total current
but the potential
difference on each branch
is going to be the same.
To find the total resistance,
you need to do one
over the resistance on each branch.
Mains electricity in the UK
is 230 volts, and 50 hertz.
Inside a plug socket, we have a fuse,
which has a very small
bit of wire going through.
We can see from the circuits
then look for a fuse wire
going all the way through.
And this wire will melt if
too much current goes through.
That's a safety feature of the plug.
We have a live wire, the earth wire,
which is another safety
feature of the plug.
The neutral wire, the
pins holding them down.
The cable grip, another safety feature,
making sure that the
wire doesn't go anywhere.
The cable, which is
double encased in plastic,
this encased in plastic,
then this encased in plastic.
Again, another safety feature of the plug,
and the plastic casing, another
safety feature of the plug.
Power is equal to potential
difference times current.
Power is measured in watts.
That is a capital W.
Potential difference is measured in V
and current is measured in amps.
Power is equal to the current squared
times the resistance.
Power is measured in watts, capital W.
Current is measured in amps,
and resistance is measured in ohms.
We've got maths in this video,
so here is a quick, little duckling break
to refresh us for a bit more revision.
Energy is equal to power times time.
energy is measured in
joules, that is capital J.
Power is measured in
watts, with a capital W,
and time, seconds, with a lowercase S.
Energy is equal to charge
times potential difference.
Energy is measured in
joules, charge is measured
in coulombs, and potential difference
is measured in volts.
The National Grid is
how we get electricity
from power stations to our houses.
The power stations
generate the electricity
and they move it to a step up transformer,
then through a network
of cables and pylons.
This gets moved towards country
to a step down transformer
and then into our houses.
Step up and step down transformers
are an important part
of our National Grid.
They work by having a
varying number of coils
on each side, depending
whether they're step up
or step down transformer.
A step up transformer
will turn a low voltage
into a high voltage, so
that the energy can move
through a system, electricity
can move through a system
with less energy loss,
making it more efficient,
whereas a step down
transformer will take it
from high voltage into low voltage
so it's safe to be in our homes.
Solid particles are in a fixed position.
They do vibrate but very, very slightly,
and it's around a fixed position.
They do not move around.
Liquid particles move
around much more festive,
touching each other, but
they're not in a fixed position.
They're moving about randomly.
It's still rather limited movement.
It's still within a confined space.
Unlike gas, which is free to move
and zip around all over the place.
If we're going to be putting energy in,
then we're going to be
turning a solid into a liquid,
or we're going to evaporating
a liquid into a gas.
If energy is coming out of the system,
a gas is gonna be condensing,
or liquid is going to be freezing.
Density is the amount
of mass in a set volume.
So, mass in a set volume.
And this is time for the equation,
and the equation for this is rho.
I know it looks like
lowercase P but it's not.
It's lowercase rho.
Equals mass over volume.
The units you need to know for this.
Mass is measured in kilograms.
Volume is measured in meters cubed,
and density is measured in
kilograms per meters cubed.
Specific heat capacity is how much energy
is needed to raise the temperature
of one kilogram of the
substance by one degree.
Our equation for that is change in energy
equals mass times specific heat capacity
times change in temperature.
Specific heat capacity
is going to be particular
to whatever substance
they're talking about,
and they will tell you this.
I wouldn't expect them to
expect you to know this.
Our units for energy are joules.
Our units for mass, kilograms.
Our units of change in
temperature are degrees C,
and specific heat capacity
is joules per kilogram,
degrees C.
There is not an extra power in here.
That is a space in there.
Specific latent heat is how much energy
is needed to change a substance
from solid to liquid at the melting point.
And remember, if a substance is pure,
it will change instantly
at one temperature.
The equation for this is energy
equals mass times specific latent heat.
Our units for this are going
to be joules for energy,
mass is going to be measured in kilograms,
and specific latent heat
is joules per kilogram.
When looking at the
collection of molecules
in a system, and the
amounts of energy they have,
we are going to have
two bell-shaped curves.
At low temperatures, there
are gonna be more molecules
that have less energy, and few molecules
that have high energy.
Now if we say that this point here
is where molecules have
enough energy to evaporate,
then only these ones at low
temperature can evaporate.
However, at high temperature,
more molecules have more energy,
so there's still going some
with a low temperature,
but the majority of them
are now gonna have a high temperature,
meaning, more of them are
gonna pass this threshold
for evaporation, and the
average kinetic energy
is going to be the area under the graph,
so as the molecules evaporate,
they're going to be leaving
this section of the graph,
so evaporation is actually going to lower
the average kinetic energy of a system.
In this video, I'm using a simulation
from the accident fact website.
You can see here, we
have a closed container,
and I'm adding in gas here,
and we can see the pressure.
As the pressuring, as more gas goes in,
we can see the pressure is increasing,
so it's stabilized, I'm gonna
add in lots more gas here,
and you can see the
pressure's going to increase.
So as the gas bumps against the walls
of the container, it's
exerting a small force,
it's doing work on there,
and it is going to be increasing
the pressure in the system.
An atom is incredibly tiny.
The word atom means uncuttable,
and it's so tiny that the
Greeks who named it atom
thought it was the smallest thing.
But it isn't the smallest thing.
We know there are things inside of it.
Now, I said it was incredibly tiny.
Its size is 0.1, so 0.5 nanometers,
which is one times 10 to the minus 10
to five times 10 to the minus 10 meters.
Now, inside our atom, we
have protons and neutrons,
and in the shells on the
outside, we have electrons.
This bit in the middle here,
this is called a nucleus.
Protons and neutrons are
located in the nucleus,
whereas electrons are in the outer shells.
Protons have a mass of one,
neutrons have a mass of one,
and electrons are incredibly tiny.
Their mass is 1/2000ths that
of mass of a proton or neutron.
Protons have a charge of plus one.
Neutrons have no overall charge,
and electrons have a charge of minus one.
On the periodic table,
you will see two numbers.
The larger number of the
two is the mass number.
The smaller number of the
two is the atomic number.
It does not matter
where these are located.
Different books, example,
are gonna put these in
different locations.
It doesn't matter where these are located.
The mass number is equal
to number of protons
plus the number of neutrons.
The atomic number is equal
to the number of protons
and also equal to the number
of electrons in an atom.
So if you want to find
the number of protons,
that is equal to the atomic number.
And if you want to find
the number of neutrons,
that is equal to the mass number
minus the atomic number.
Here we have boron, the mass number is 11.
The atomic number is five, so
if you want to find the number
of neutrons, that is mass minus atomic,
11 minus five gives us six.
Protons equal five, electrons equal five.
Now, protons have positive charge,
one, two, three, four, five.
Electrons have a negative charge,
one, two, three, four, five.
So an atom, and this is for an atom only,
will have the same number
of positive charges
and negative charges, which means
there is going to be no
overall charge in an atom.
An ion is going to have
lost or gained electrons.
So for example, if we have
our, take our boron again,
we've got one, two, three,
four, five positive,
and one, two, three, four,
five negative charges.
If it loses an electron, it now no longer
has the same number of
positive and negative charges,
so it's going to be charged.
It has created an ion.
Here we have two isotopes of carbon.
You can see they have the
same atomic number, six,
but different mass numbers,
which means each of them
is going to have six protons.
They're each going to have six electrons,
but when it comes to the mass number,
one of them has 12 minus six.
Six neutrons, and one of
them has 14 minus six.
Eight neutrons.
An isotope is an atom
that has a different number of neutrons.
The model of the atom has
changed a lot over time,
and it's changed because
we have new developments
and new discoveries.
From Ancient Greece, when
they developed the word,
atom, uncuttable, to Dalton,
where it was a solid sphere.
JJ Thompson, who discovered electrons,
where we had a plum pudding model,
a positive sphere with negative
bits dotted throughout.
Rutherford, who did the
plum pudding experiment
and worked out that it had a solid center.
Bohr, who developed the
nuclear model of the atom.
Now, I know the writing's
very small in here.
That's 'cause you don't need
to know the exact details.
You just need to know
the overall developments.
Rutherford gave us the positive center,
which we call the nucleus.
Chadwick added in neutrons,
and then Bohr developed
this nuclear model that we use today.
With a positive center, and
electrons orbiting outside.
Rutherford wanted to test
the plum pudding model,
which was a large positive blob
with negative bits dotted throughout it.
So he took a sheet of gold foil,
and a gun that fired out particles,
and he shot them at
the sheet of gold foil.
Now the majority of these
particles went straight through,
but very occasionally, one would
get deflected a little bit,
and even more occasionally,
one would get deflected a lot,
and this told Rutherford
that instead of it
being an evenly distributed
pattern of negative
and positive charges, we are likely
to have an overall buildup
of positive in the middle,
with negative charges around the outside,
so that the majority of the atom
was made up of empty space, and this led
to the development of the
nuclear model of the atom.
There are three types of radiation.
Alpha radiation, beta
radiation, and gamma radiation.
Alpha radiation is also
known as a helium nuclei.
Beta radiation is also
known as an electron.
And gamma radiation is part of
the electromagnetic spectrum
is a wave.
A helium nuclei, an alpha radiation,
can be written as alpha
four two, mass of two,
positive charge of, mass of
four, positive charge of two.
An electron can be written in E,
mass of zero, charge of minus one.
And gamma is, again, just a wave.
Alpha radiation is very large,
whereas gamma radiation is very small.
Alpha radiation is highly ionizing,
whereas gamma radiation is not.
Ionizing means how good it
is at knocking electrons off,
so how good it is at turning
something into an ion.
Gamma radiation is highly penetrating,
whereas alpha is not.
To stop alpha radiation, a bit of paper
or a bit of skin will do it.
Aluminum foil or tin foil
will stop beta radiation,
but thick lead is needed
to stop gamma radiation.
A Geiger-Muller tube
will measure radiation.
It generally clicks every time
it hears a bit of radiation.
And the unit for radiation
is the becquerel.
A half life is the time it takes
a half the radioactive atoms
to decay into something else.
We can use that as a graph
if we take 100%, and 50%.
Read across, with a ruler, and down, 50%,
across with a ruler, and
down, and that there,
the time between having 100%
activity and 50% activity,
or whatever value, and half
of whatever that value is
is going to be the half life.
The half life is something that can range
between very quick milliseconds,
to thousands or hundreds of years.
The calculations for this are
a lot simpler than they look.
Here we have uranium 238 is
going to get alpha decay.
Alpha is four two.
So we have 238 minus four gives us 234.
92 minus two gives us 90.
Then we need to use
periodic table to look up
what has an atomic number of 90.
Giving us thorium.
For beta decay, we have minus beta.
Zero minus one.
238 minus zero gives us 238.
92 minus minus one gives us 93,
which gives us neptunium.
It does not matter about the mass number
of these calculations.
The atomic number is the important thing.
Different isotopes of an element
are going to have different half lives.
If you are doing Combined Science,
this is the end for you.
Excellent work, well done
on making it this far.
If you are doing Physics,
you need to keep going
for just a tiny bit longer.
If we want to work out the
pressure in the system,
that is volume times a constant.
The constant, you'll be told in the exam.
Our units for pressure are pascals.
Our units for volume are meters cubed.
When we have static electricity,
we have an object that
isn't normally being charged
becoming charged.
That happens when two
insulators rub together.
This is caused by the
movement of electrons
from one thing to another thing,
and you're going to get a shock
when the charges reset and
when you touch something metal.
If you have two charged
objects coming together,
they're going to repel each other.
Alternatively, if you
have a charged object,
and an object which has
the opposite charge,
they're going to attract each other.
You need to know all of
the different sources
of background radiation.
Now, the majority of background radiation
comes from radon gas.
This is about 50 cents,
and this picture here
shows a beautiful scene
from down in Cornwall,
down in Devon, 'cause that area
has a lot of radon gas going on.
Then we have medical, and about 14%
comes from medical x-rays.
And different medical treatments
such as x-rays or CT scans.
Then, we have stuff that
comes up from the ground.
This, again, is about 14%.
Then we get slightly smaller,
and these are the sort
of things that you really can't avoid,
because you do get some
background radiation
from food and drink,
and this is about 11.5%.
Moving on to slightly smaller amounts now,
cosmic radiation, radiation
that we get from space,
is going to be about 10%.
Even smaller amounts now, from
testing of nuclear weapons,
it is going to be about 0.2%.
From plane travel, and this obviously,
varies between person,
'cause the more you travel
on a plane, the more radiation
you are going to be exposed to.
And then the last one,
we're all gonna get a teeny,
tiny little dose from
nuclear power stations.
And those are your sources
of background radiation.
The uses of radioactivity
are quite varied,
and what (mumbles) radioactivity
you're going to use
is going to depend on the half life,
and it is going to depend
on the type of radiation.
Gamma radiation can be
used for cancer treatment
and sterilizing materials
'cause it is very good
at killing cells.
It is going to be in a
bit of medical equipment.
We're going to need it to
have a very long half life.
Beta radiation can't get very far,
so it just the things that
need a short distance.
For example, testing the thickness of foil
that's being made, or
copper that's being made.
If too much beta radiation gets through,
the window is too thin, if
not enough gets through,
the window is too thick.
For this, we need a long half life,
because it's in the industry,
whereas for medical
tracer, we don't want it
to have long half life.
We want it to get out of the
body as quickly as possible.
Alpha radiation is used in smoke alarms
and this, again, we want it
to have a long half life.
In nuclear fission, the breaking apart
of atoms, we have a chain reaction.
The first neutron is
fired out of something,
and it hits our heavy,
heavy radioactive element,
whether that's uranium or plutonium,
and it doesn't really
matter for this instance.
It splits it and we are going to get,
the example I'd like you to
draw three neutrons coming out,
so neutrons coming out,
some radiation coming out,
and some smaller atoms.
The neutrons that come out can then go on
and hit other nuclei, so it keeps going,
and every single reaction
releases a neutron,
which can go on and hit something else,
which is why it's called a chain reaction.
These nuclei, once they
hit, they break down
into smaller nuclei, release
neutrons, and radiation.
Nuclear fusion is a process
that takes place in our stars.
It is going to be where
nuclei fuse together
to make one nuclei, one large nuclei.
It's gonna be combined
with the release of energy,
whether this is going to be light,
heat, or sound, or all three,
in the case of our star.
("Something Elated" by Broke for Free)
