GCSE Physics 2.0

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Anything that moves has energy
in its kinetic energy store
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When is energy transferred to this store
when an object speeds up
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When is energy transferred away from this store
when an object slows down
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The energy in the kinetic energy store depends on
the objects mass and speed
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The greater the mass and the faster its going
The more enrgy there will be in its kinetic energy store
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What is the formula for kinetic energy
KE = 1/2 x Mass x Velocity/ speed squared
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Raising objects store energy
in Gravitational potential energy stores
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Lifting an object in a gravitational field
requires work. This causes a transfer of energy to the GPE store of the object
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The higher the object is lifted
the more energy is transferred to this store
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What is the formula for GPE
GPE = Mass x Gravitational field strength x Height
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When something falls
energy from its GPE store is transferred to its kinetic energy store
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For a falling object when there's no air resistance
Energy lost from the GPE store = Energy gained in the kinetic energy store
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Air resistance acts
against all falling objects- it causes some energy to be transferred to other energy stores
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Work done is
Energy transferred
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More energy needs to be transferred to the
thermal energy store of some materials to increase their temperature than others
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Materials that need to gain lots of energy in their thermal energy stores to warm up also
transfer loads of energy when they cool down again. They can store a lot of energy
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What is specific heat capacity
The amount of energy needed to raise the temperature of 1kg of a substance by 1 degree celsius
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What is the equation that links energy transferred to specific heat capacity
change in thermal energy = Mass x Specific heat capacity x Temperature change
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What is the first step for investigating specific heat capacities
You'll need a block of the material with two holes
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What is the second step for investigating specific heat capacities
Measure the mass of the block then wrap it in an insulating paper to reduce the energy transferred from the block to the surroundings. Insert the thermometer and heater.
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What is the third step for investigating specific heat capacities
Measure the initial temperature of the block and set the potential difference of the power supply to be 10v. Turn on the power supply and start a stop watch
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What is the fourth step for investigating specific heat capacities
When the power is on the current in the circuit does work on the heater, transferring energy from the power supply to the heaters thermal energy store
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What is the fifth step for investigating specific heat capacities
As the block heats up take readings of the temperature and current every minute for 10 minutes
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What is the sixth step for investigating specific heat capacities
When you've collected enough readings turn off the power supply. You can calculate the power
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How do you calculate power
potential difference X current
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How do you calculate the energy transferred to the heater
Power x time in seconds
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What is conduction
The process where vibrating particles transfer energy to neighbouring particles
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What is convection
Where energetic particles move away move away from hotter to cooler regions
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What is internal energy
The total energy that its particles have in their kinetic and potential energy stores
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The particles in a system
vibrate or move around - they have energy in their kinetic energy stores
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They also have energy in their
potential energy stores due to their positions
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Heating the system transfers
energy to its particles increasing the internal energy
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What does this lead to
A change in temperature or a change in state
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If the temperature changea
the size of the change depends on the mass of the substance , what its made of and the energy input
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A change in state occurs
if the substance is heated enough- the particles will have enough energy in their kinetic energy stoes to break the bonds holding them together
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The particles in a gas are
constantly moving with random directions and speeds
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If you increase the temperature of a gas
you transfer energy into the kinetic energy stores of its particles
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As gas particles move about high speeds
they bang into each other and what else happens to be in the way
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When they collide with something
They exert a force on it.
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In a sealed container
the outward gas pressure is the total force exerted by all of the particles in gas
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Faster particles and more frequent collisions both lead to
an increase in net force & so gas pressure
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Increasing the temperature
will increase the speed and so the pressure (if volume is kept constant)
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If temperatue is constant increasing the volume of a gas means
the particles get more spread out and hit the container less often. The gas pressure decreases
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Pressure and volume are inversely proportional meaning
when volume goes up pressure goes down
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What is the formula for constant
pressure x volume
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The pressure of a gas causes a
net outwards force at right angles to the surface of its container
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There is also a force
outside of the container due to the pressure of the gas around it
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If a container can easily change its shape (e.g. a balloon)
Then any change in these pressures will cause the container to compress or expand due to the overall forces
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If you transfer energy by applying a force
then you do work
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Doing work on a gas
increases its internal energy which can increase its temperature
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What are the two types of electricity supplies
alternating current (ac) & direct current (dc)
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in ac supplies the current is
constantly changing direction
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Alternative currents are produced by
alternating voltages in which the positive and negative ends keep alternating
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The UK mains supply (home electricity)
is an ac supply at around 230 V
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The frequency of the ac mains supply is
50 cycles per second or 50 Hz (hetrz)
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Cells and batteries supply
direct current (dc)
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Direct current is a current that is
always flowing in the same direction.
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What is Direct current created by
a direct voltage
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Most electrical appliances are connected to the mains supply
By three core cables
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What do the three wires have each
A core of copper and a coloured plastic coating
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The colour of the wire
shows its purpose
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What are the colours of the wires
Brown, Blue, green and yellow
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Talk about the brown wire
Live wire- This provides the alternating potential difference. At about 230 V
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Talk about the blue wire
The neutral wire completes the circuit and carries away current It is around 0 V-
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Talk about the green and yellow wire
Its for protecting the wiring and for safety. It stops the appliance casing from being live. No current unless there's a fault 0v
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Where does electricity normally flow
in through the live wire and out through the neutral wire
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Your body and the earth is at
0 V
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If you touch the live wire
a large potential difference is produced across your body and a current flows through you
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What does this cause
This could injure or even kill you
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Any connection between live and earth
can be dangerous
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if the link creates a low resistance path to earth
A huge current will flow , which could result in a fire
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What is the national grid
A giant system of cables and transformers that covers the UK and connects power stations to consumers
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The national grid transfers
electrical power from power stations anywhere on the grid to anywhere on the grid where it's needed
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Throught the day electricity usage
changes
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Power stations have to produce
enough electricity for everyone to have it when they need it
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Demand increases when
people wake up. come home. when it gets cold or dark or when popular events are on TV
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Power stations often run at well
below their maximum power outut so theres spare capacity to cope with a high demand
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To transmit the huge amount of power needed
You need either a high potential difference or a high current
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What is the problem with a high current
you loose alot of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings
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Its cheaper to
boost the pd up really high and keep the current as low as possible
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For a given power increasing the pd
decreases the current which decreases energy lost. This makes the national grid an efficient way of transferring energy
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To get a high potential difference to transmit power requires
transformers and big pylons with huge insulators
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Other cards in this set

Card 2

Front

When is energy transferred to this store

Back

when an object speeds up

Card 3

Front

When is energy transferred away from this store

Back

Preview of the front of card 3

Card 4

Front

The energy in the kinetic energy store depends on

Back

Preview of the front of card 4

Card 5

Front

The greater the mass and the faster its going

Back

Preview of the front of card 5
View more cards

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