Physics AQA Gcses Paper 1

what are the eight energy stores?

• thermal

• kinetic

• gravitational potential

• elastic potential

• chemical

• magnetic

• electrostatic

• nuclear

how can energy be transferred?

• mechanically (force doing work)

• electrically (work done by moving charges)

• by heating

• by radiation (light, sound etc)

what happens when a system is changed?

(system is a single object/group of objects)

energy is transferred

(into or away from the system, between different objects in the system or different energy stores)

what are closed systems?

systems where neither matter nor energy can enter or leave

(the net change in the total energy of a closed system is always zero)

how can energy be transferred by heating?

water in a kettle:

energy is transferred electrically to the thermal component of the kettle, which transfers energy by heating to the water’s thermal energy store

what are examples of doing work?

• initial force of throwing a ball upwards (chemical - kinetic)

• gravitational force of dropping a ball (gravitational potential - kinetic)

• friction between car brakes + wheels as it slows down (kinetic energy - thermal in the surroundings)

• collision between car and solitary object (kinetic - other)

what has kinetic energy and what does this depend on?

• anything that is moving - energy is transferred TO this store when an object speeds up and transferred AWAY when an object slows down

• the energy in the kinetic store depends on the object’s mass + speed - greater the mass and the faster it’s going, the more energy there will be in this store

what has gravitational potential energy and what does this depend on?

• raised objects - lifting an object in a gf requires work, which -causes a transfer to the gpe store of the object (the higher the object is lifted, the more gpe it has)

• the energy in the gpe store depends on the object’s mass, its height and the strength of the gravitational field

what energy transfers happen when something falls?

gravitational potential energy store → kinetic energy store

energy lost from gpe store = energy gained in kinetic store (with no air resistance)

air resistance causes some energy to be transferred to other stores (e.g thermal)

what is specific heat capacity?

specific heat capacity is how hard it is to heat something up

(different materials have different specific heat capacities eg. water needs 4200J to warm 1kg by 1C but mercury only needs 139J)

REQUIRED PRACTICAL - investigating specific heat capacities

1. you will need a block of chosen material with two holes in it (for heater and thermometer to go in)

2. measure the mass of the block and wrap it in an insulating layer, then insert the heater and thermometer

3. measure the initial temperature of the block, set the voltage of the power supply to be 10V, then turn on the power supply and start the stopwatch

4. as the block heats up, take readings of the temp and current, every minute for 10 minutes

5. use P = VI to calculate the power supplied to the heater

6. calculate how much energy has been transferred to the heater using E = Pt (t is the time in seconds since it began)

7. plot a graph based on the results, and then find the gradient of the straight part (temp change / change in thermal energy)

8. the specific heat capacity of the material is 1/ (gradient x mass of the block)

what is the conservation of energy principle?

energy can be transferred usefully, stored or dissipated, but cn never be created or destroyed

what is power?

power is the rate of energy transfer, or the rate of doing work

power is measured in watts (one watt = one joule of energy transferred per second)

a powerful machine is one which transfers a lot of energy in a short space of time

what is conduction + where does it occur?

the process where vibrating particles transfer energy to neighbouring particles - occurs mainly in solids

(particles in an object being heated vibrate and collide with each other, causes energy to be transferred between particles’ kinetic energy stored - thermal conductivity is how quickly this happens)

what is convection + where does it occur?

where energetic particles move away from hotter to cooler regions - occurs only in liquids and gasses

(similar to conduction, but unlike in solids, particles in liquids and gases are able to move - when heated particles move faster and space between them increases, density decreases - warmer and less dense region will rise above cooler denser regions)

how can we reduce unwanted energy transfers?

• lubrication - reduces frictional forces

• insulation - reduces rate of thermal transfer

what is efficiency?

most energy transfers involve some waste energy - the less energy that is wasted, the more efficient the device is

useful energy output is not equal to total energy input as no device is 100% efficient (usual wasted energy → unwanted thermal stores)

what are non-renewable energy sources?

• fossil fuels - oil, coal, natural gas

• nuclear fuel - uranium, plutonium

these will run out some day and do damage to the environment, but they are reliable

what are renewable energy sources?

• solar

• wind

• waves

• tides

• hydro-electricity

• biofuel

• geothermal

these will never run out, they do less damage to the environment but are less reliable and don’t provide as much energy

wind, solar and geothermal resources

• wind - turbine that have a generator in them, the spinning blades generate electricity

• solar cells - depends on solar rays, so only can be used in the daytime

• geothermal power - uses underground thermal stores in volcanic areas (slow decay of radioctive elements) - reliable

hydro-electricity, waves and tides

• hydro-electricity - falling water in valleys using dams -

• waves - wave powered turbines

• tidal barrages - uses the sun and moon’s gravity

bio-fuels and non-renewables

• bio-fuels - made from plants and waste - large costs

• non renewables - reliable but cause environmental problems such as carbon dioxide released into the atmosphere when fossil fuels are burnt - nuclear waste is dangerous and potential major catastrophe

what is current?

the flow of electrical charge

(current can only flow with a source of potential difference, in a closed circuit current has the same value everywhere, measured in amperes - A)

what does the total charge in a circuit depend on?

current and time - the size of the current is the rate of flow of charge

what is an ammeter?

it measures the current (in amps) flowing through a wire

must be placed in series with whatever you’re investigating

what is a voltmeter?

it measures the potential difference (in volts) across a wire

must be placed in parallel with whatever you’re investigating - not around any other bit of of the circuit (e.g battery)

REQUIRED PRACTICAL - resistance and wire length

1. attach a crocodile clip to the wire level with 0cm, then attach a second crocodile clip a certain distance away from the first (e.g 10 cm)

2. close the switch, then record the current through the circuit through the wire and the pd across it

3. open the switch and move the second clip another distance along the wire, then close it and record current and pd again

4. repeat this for a number of lengths of the test wire

5. use measurements of current and pd to calculate resistance using R = V / I for each length of wire

6. plot a graph of resistance against wire length and draw a line of best fit, graph should be a straight line through origin

what are ohmic conductors?

components of a circuit that have a constant resistance (not changed as the current is changed)

e.g a wire or resistor

REQUIRED PRACTICAL - I-V characteristics

1. set up a test circuit with a battery, variable resistor, voltmeter, ammeter and a component that you will change

2. begin to vary the variable resistor - alters the current flowing through the circuit and pd across the component

3. take several readings from the voltmeter and ammeter to see how the pd varies as the current changes

4. swap over the wires connected to battery so the current is reversed and take readings

5. plot a graph of current against voltage for the component

what is the I-V characteristic for a filament lamp?

as the c__urrent increases__, the temperature of the component increases, so the resistance increases - means less current can flow per unit pd - graph gets shallower, hence the curve

what is the I-V characteristic for an ohmic conductor?

the current through this conductor is directly proportional to potential difference - straight line

what is the I-V characteristic for a diode?

current will only flow through this component in one direction - the diode has very high resistance in the reverse direction

what is an LDR?

light dependant resistor - dependant on the intensity of light

bright light - resistance falls

darkness - resistance is highest

what is a thermistor?

temperature dependant resistor

hot conditions - resistance drops

__coo__l conditions - resistance goes up

what is a series circuit + what happens to resistance, pd and current?

different components are connected line to line, end to end between the +ve and -ve of the power supply - if you remove/disconnect a component, the circuit is broken

• current - the same everywhere

• pd - shared - pds around the circuit always add up to the source pd

• resistance - adds up - total resistance of two components is the sum of their resistances

what is a __paralle__l circuit + what happens to current, pd and resistance?

each component is separately connected to the +ve and -ve of the power supply - if you remove one component, it will hardly affect the others at all

• current - shared between branches - total current is equal to the total of all currents through the separate component

• pd - same across all components

• resistance - adding a resistor in parallel reduces the total resistance

REQUIRED PRACTICAL - investigating adding resistors in series

1. find at least four identical resistors - build a circuit with a battery, ammeter and resistor

2. make note of pd and measure current to calculate resistance

3. add another resistor and measure current and pd to calculate resistance with the added resistor

4. repeat until you have added all your resistors

5. plot a graph of the numbers of resistance against the total resistance of the circuit

REQUIRED PRACTICAL - investigating adding resistors in parallel

1. use the same equipment as in series and build the same initial circuit

2. measure total current and calculate resistance again

3. add another resistor in parallel with the first

4. measure total current and pd of the battery to calculate the overall resistance of the circuit

5. repeat until you have added all your resistors in parallel

6. plot a graph of numbers of resistors against the total resistance

what are the two supplies of electricity in the home?

• ac - alternating current - constantly changing direction, produced by alternating voltages, - mains supply

• dc - direct current - flowing in the same direction, produced by direct voltage - batteries and cells

what is the frequency and potential difference of the UK mains supply?

• frequency - 50Hz

• potential difference - 230V

what are the three separate wires in a plug?

• live - brown - provides the alternating pd from the mains supply - 230V

• neutral - blue - completes the circuit, current flows through the live and neutral wires - 0V

• earth - green and yellow - protecting the wiring, stops the appliance from becoming live if faulty - 0V

what is static electricity and how is it caused?

• when certain insulating materials are rubbed together, negatively charged electrons will be scraped off one material and dumped on the other

• this leaves the materials electrically charged, with a positive or negative charge on the two materials

• which way the electrons are transferred depends on the two materials involved

• they cause a shock or spark when moved

what creates an electric field?

electric charges:

• an electric fields is created around any electrically charged object

• the closer you get, the stronger the force is

• you can show an electric field around an object using field lines

what happens when a charged object is placed in an electric field?

1. it feels a force

2. the force causes attraction or repulsion

3. the force is caused by the electric fields of each charged object interacting with each other

4. the force on an object is linked to the strength of the electric field it’s in

5. as you increase the distance between charged objects, the strength of the field decreases and the force between them gets smaller

what causes sparking?

1. when there is a high enough pd between a charged object and the earth/an earthed object

2. a high pd causes a strong electric field between the charged and the earthed object

3. the strong electric field causes electrons in the air particles to be removed (known as ionisation)

4. air is normally an insulator,but when it is ionised it is much more conductive, so a current can flow through it - sparks

what is density?

a measure of the compactness of of an object - relates the mass to how much space it takes up - in a dense object particles are packed tightly together

what are the three states of matter?

• solid - fixed, regular particles that don’t have much energy, density is highest, strong forces of attraction between particles

• liquids - particles are close together, can move past each other and form irregular arrangements, more energy than solid, weaker forces between particles, less dense

• gas - free to move in random directions at high speeds, low density, more energy than liquids and solids, almost no forces between particles

REQUIRED PRACTICAL - investigating density in solids

1. use a balance to measure its mass

2. regular solid - measure its length, width and height, then calculate its volume

3. irregular solid - submerge in a eureka can filled with water, and it will transfer the displaced water by the solid into a measuring cylinder - this is the volume of the solid

4. use the its volume and mass to calculate the density

REQUIRED PRACTICAL - investigating density in liquids

1. place a measuring cylinder on a balance and zero it

2. pour 10ml into the cylinder, repeating until the cylinder is full and measure the mass and volume each time

3. use the density formula

what is internal energy?

energy stored by the particles making up a system

• they have energy in their kinetic energy stores as particles vibrate

• also have gpe depending on their positions

• heating the system transfers energy to its particles so increases the internal energy

what is specific latent heat?

the energy needed for a 1kg mass of a material to change state without changing its temperature

• for cooling, it is the energy released by a change of state

• between a solid and a liquid - slh of fusion

• between a liquid and a gas - slh of vaporisation

what creates pressure in a gas?

colliding gas particles:

• when collision happens a force is exerted

• increasing temperature will increase the pressure (if volume is kept constant)

• pressure and volume are inversely proportional

• pV = constant

what are isotopes?

different forms of the same element but with a different number of neutrons - atomic mass increases

what are alpha particles + alpha radiation?

a helium nucleus - 2 protons + 2 neutrons

• alpha radiation is when a helium nucleus is emitted from an atom

• __strongl__y ionising

• not very penetrative - stopped by paper

what are beta particles + beta radiation?

high speed electron released by the nucleus

• moderately ionising

• moderately penetrative - stopped by aluminium foil

• for every beta particle emitted, a neutron in the nucleus has turned into a proton

what is gamma radiation?

electromagnetic waves with a short wavelength

• weakly ionising

• very penetrative + can travel long distances - stopped by thick lead or concrete

what happens to the nucleus during alpha decay?

changes the mass of the nucleus

• atomic number reduces by 2

• mass number reduces by 4

what happens to the nucleus during beta decay?

increases the charge

• a neutron changes into a proton

• an __electro__n is released

• atomic number increases

• mass number does not change

what is half-life?

time taken for the number of radioactive nuclei in an isotope to halve

• short half-life - activity falls quickly - less dangerous

• long half-life - activity falls slowly - more dangerous

what are the sources of background radiation?

• radon gas

• rocks (uranium salts in graphite)

• food (bananas)

• cosmic rays

• radioactive waste or fallout

what is irradiation?

exposure to radiation - irradiating something does NOT make it radioactive

what is contamination?

unwanted radioactive atoms getting onto/into an object - contaminating atoms might then decay, releasing harmful radiation

what are the uses of radiation?

• radiotherapy - cancer cells killed by ionising radiation

• medical tracers - iodine-123

what are the risks of radiation usage?

• can enter living cells and ionise atoms and molecules within them - causes tissue damage

• high doses can kill many cells at once, causing radiation sickness

what is nuclear fission?

the splitting of a large, unstable nucleus

1. the atom has to absorb a neutron before splitting

2. atom splits and forms two lighter elements

3. two or three more electrons are released when an atom splits, causing a chain reaction - the energy produced from this heats water which turns turbines

4. uncontrolled causes lots of energy - nuclear weapons

what is nuclear fusion?

the joining of two small nuclei

1. two light nuclei collide at a high speed to create a larger, heavier nucleus

2. heavier nucleus does not have as much mass as the two separate nuclei

3. fusion releases lots of energy

4. fusion happens in stars with helium and hydrogen

Definition of a wave

Waves carry energy or information from one place to another

Transverse waves

e.g. light waves

Travel perpendicular to the direction of energy travel

Up and down movements

Longitudinal waves

e.g sound waves

Travel parallel to the direction of energy travel

Across movements

What is the term for short and long wavelengths in a Longitudinal Wave

Short: compression

Long: Rarefaction

What frequency can humans hear?

20 - 20,000 Hz

Definition of Frequency

The number of waves passing a point in a second

Definition of ‘period’

P - time period

Time taken to pass a point (seconds)

Time taken for one complete oscillation

Variables for the speed of ripples on water practical

Control - Travel length, height dropped from

Dependant - Time to travel 2m

Independent- Water Depth

Equation for speed

S=D/T

Speed = Distance / Time

What is the ‘normal’?

A line drawn perpendicular to the mirror/surface to help measure the angle

When light reflects off a flat surface in a straight line, what is this called?

specular

When light reflects off a rough surface in different directions, what is this called?

Diffused

Info about sound waves

• Longitudinal (across)

• Vibrations travel through air

• Vibrations move to our ear drums which vibrate and cause the sensation of sound

Ultrasound

• Above 20,000Hz (above human hearing)

• Wave is partially reflected at the boundary between materials

What is ultrasound used for and how does it work?

Medical (foetus scan) - Sound waves bounce off skin, organs etc at different speeds. These echos are converted into images with a transducer.

Industrial (under oceans) - Time taken for reflections to reach a detector can be used to determine how far away a boundary is

Dog training (whistles)

S - waves

Secondary Waves

Transverse

Can’t travel through liquid

P - waves

Primary Waves

What is the Electromagnetic spectrum?

Moves energy from a source to an absorber

Lowest Freq:

Radio waves

Microwaves

Inferred Radiation

Visible light

Ultraviolet

X-ray

Gamma waves

Highest Freq

Wavelength

The distance from a point on a wave to the equivalent point on the next wave

(metres)

What Is the highest and lowest point on a wave called?

Peaks

Troughs

What can happen when a wave meets a boundary

Reflection

Transmission

Absorption

Refraction

What happens when waves are reflected off a surface

The angle of incidence is equal to the angle of reflection

What does Refracted mean?

Wave is reflected off a surface and changes direction

What happens when light travels from a material with a low to one with higher refractive index?

The light bends towards the normal

What happens when light travels from a material with a high to one with lower refractive index?

The light bends away from the normal

Why does Refraction happen?

• When a light wave enters a medium in which it travels slower at an angle,

• The first part of the wave to enter slows down

• The rest continues at a higher speed

• the waves changes direction towards the normal

Label this ripple tank

Wave speed equation

v=f x λ

wave speed = freq x wavelength

Label this diagram

How to determine wavelength with this practical

Total Length / number of half wavelengths x 2

How to draw the reflected ray?

What is a convex lens?

How do you show this?

Method for angle of refraction with ray box

• place a glass block on a piece of paper
• draw around the glass block
• use the ray box to shine a ray of light through the glass block
• mark the ray of light entering the glass block
• mark the ray of light emerging from the glass block
• join the points to show the path of the complete ray through the block
• and draw a normal line at 90 degrees to the surface
• use a protractor to measure the angle of incidence
• use a protractor to measure the angle of refraction
• use a ray box to shine a ray of light at a range of different angles (of incidence) • increase the angle of incidence in 10 degree intervals
• from an angle of incidence of 10 degrees to an angle of incidence of 70

degrees.