physics paper 1

name the 4 pathways of energy transfer

mechanical, electrical, heating, radiation

name the 8 energy stores

kinetic, chemical, nuclear, magnetic, elastic potential, gravitational potential, thermal, electrostatic

order of unit conversion

nano, (divide by 1000), micro, (divide by 1000), milli, (divide by 10), centi, (divide by 10) deci, (divide by 10), meter, (divide by 1000), kilo, (divide by 1000), mega

what must you remember to do if the unit is squared or cubed?

divide or multiply by the square or square root

1 joule =?

1 newton meter

specific heat capacity

the amount of energy needed to raise the temperature of 1kg of the substance by 1 degree C

REQUIRED PRACTICAL 1: specific heat capacity

• place a beaker on a balance and tare it, then add 1kg of oil

• use a thermometer to determine and record initial temperature

• insulate the beaker to reduce thermal energy lost to surroundings

• connect joulemeter and power pack to immersion heater and turn it on

• leave for 30 mins for temp to rise

• read Joules passed into the heater and the final temp of the oil

  • rearrange and calculate specific heat capacity: change in thermal energy= mass x specific heat capacity x temperature change (J/kg°C)

sources of inaccuracy- specific heat capacity practical

• thermal energy released to surroundings- use less conductive insulator

• not all thermal conductivity into oil- ensure fully submerged

• incorrectly reading thermometer- use electronic temperature probe

• thermal energy not spread throughout oil- stir the oil

what is power?

the rate at which energy is transferred or the rate at which work is done

equation and units for power

power = work done or energy transferred / time

power in watts

energy transferred and work done in joules

time in seconds

conservation of energy

energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed

how to reduce unwanted energy transfers

lubrication, thermal insulation

correlation between thermal conductivity and energy transfer

the higher the thermal conductivity, the higher the rate of energy transfer by conductivity

correlation between thickness and thermal conductivity of a buildings walls, and the rate of cooling

the thicker the walls, the slower the cooling

the lower the conductivity, the slower the cooling

REQUIRED PRACTICAL 2- THERMAL INSULATORS

TYPE OF INSULATOR

• place a small beaker inside a larger beaker

• boil water in a kettle and pour 80cm cubed into small beaker- record initial temp and ensure is the same for each variation

• use cardboard as a lid for the large beaker, with a hole for the thermometer- bulb in the water

• record temp every 3 mins for 15 mins

• repeat with same volume of water, with insulating material like bubble wrap between the 2 beakers- ensure a range of materials, like tinfoil, polystyrene, and cotton wool

• ensure same mass of insulating material

• plot cooling curves- will cool slowest with most effective insulator

THICKNESS OF INSULATOR

• 80cm cubed of water into beaker- ensure same volume and starting temp

• temp every 3 mins for 15 mins

• repeat experiment with 2 layers of newspaper, then 4, then 6

• plot cooling curve- more layers is more insulating

efficiency equations

efficiency = useful power output / total power input

efficiency = useful output energy transfer / total input energy transfer

how to increase efficiency of an energy transfer?

• reduce friction with lubricants

• thermal insulation

Earth’s main energy resources

• fossil fuels, like coal, oil, and gas

• nuclear, biofuel, wind, hydroelectric, geothermal, tidal, solar

renewable vs non-renewable

renewable can be replenished as it is used, while non-renewable is finite

uses of energy resources

transport, heating, electricity generation

open switch

closed switch

cell

battery

diode

resistor

variable resistor

LED

lamp

fuse

voltmeter

ammeter

thermistor

LDR

what does a circuit need to include for a charge to flow?

• source of potential difference

• closed switch

equation and units for charge flow

charge flow = current x time

charge flow in coulombs

current in amps

time in seconds

current across a closed loop is…..

the same value at any point

what does current through a component depend on?

the resistance of the component and the potential difference across the component

correlation between resistance and current in a circuit

the greater the resistance, the smaller the current for a given potential difference

equation and units for potential difference

potential difference = current x resistance

potential difference in volts

current in amps

resistance in ohms Ω

REQUIRED PRACTICAL 3- RESISTANCE ACROSS A WIRE

LENGTH OF A WIRE

• tape wire to metre rule and connect at desired length to circuit with crocodile clips- every 10cm- FLYING LEAD

• set voltage of power pack at 4V to avoid overheating- DC power supply

• attach an ammeter in series, and a voltmeter in parallel

• with distance increasing in 10cm increments, record potential difference and current

• calculate resistance- V = I x R

• repeat for mean and plot

RESISTORS

• calculate resistance with a single resistor in series, and increase number of resistors each time- V = I x R

• more resistors increases resistance but decreases current

• repeat with resistors in parallel- will reduce total resistance value by a smaller fraction each time

diode iv graph

current flows in one direction only. high resistance in reverse direction

filament lamp iv graph- resistance increases as temperature increases

ohmic conductor or resistor iv graph

current is directly proportional to potential difference across resistor

explain a thermistor

• resistance decreases as temperature increases

• used in thermostats- when it gets too hot, resistance decreases and current increases, cooling it down

  • as it cools down, resistance increases- current decreases and it warms up

explain an LDR

• resistance decreases as light intensity increases

• it gets dark, and resistance increases, decreasing current, turning on lights

  • as it gets brighter, resistance decreases, which increases current, turning off lights

REQUIRED PRACTICAL 4- CURRENT AND POTENTIAL DIFFERENCE CHARACTERISTICS- RESISTORS

• set up circuit with a battery connected by wires to a resistor, which should be in series with an ammeter and a variable resistor

• add a voltmeter in parallel across a resistor

• use voltmeter to read potential difference across the resistor, then use ammeter to read current through resistor

• record in table

• adjust variable resistor and repeat a few times

• switch direction of battery to switch direction of potential difference (ammeter and voltmeter now have negative values)

• take several readings adjusting variable resistor

• plot graph of current against potential difference- directly proportional, so a resistor is an ohmic conductor

• temp of resistor must be constant- break circuit occasionally too cool down.

FILAMENT LAMP

• repeat, with resistor replaced with lamp

DIODE

• repeat, but with milliameter, resistor, and diode.

all results graphs will align with their IV characteristic graph

describe characteristics of circuits connected in series

• same current through each component

• total potential difference is shared between components

• total resistance of 2 components is the sum of the resistance of each component

  • Rtotal = R1 + R2

describe characteristics of components connected in parallel

• pd across each component is the same

• total current through whole circuit is the sum of currents through separate components

  • the total resistance of 2 resistors is less than the resistance of the smallest individual resistor

describe the difference between series and parallel circuits

series- one path for current flow- all components connected to a single loop

parallel- multiple branches- current can split and take different routes

why does resistance increase in series but decrease in parallel

• SERIES- one pathway for current to flow- each component is a new obstacle, so resistances add together

  • PARALLEL- more pathways for current to flow- as current increases, resistance decreases- V = I x R

is mains electricity AC or DC?

AC

domestic electricity supply frequency

50Hz

domestic electricity supply voltage

230V

live wire colour and purpose

brown- carries alternating potential difference from the supply

neutral wire colour and purpose

blue- completes the circuit

earth wire colour and purpose

green and yellow stripes- safety wire- prevent the appliance becoming live

voltage of each wire in a plug

earth- 0v, unless there is a fault

neutral- 0v

between live and earth- 230v

why might a live wire be dangerous even with an open switch in the mains circuit

it still carries a continuous voltage- an open switch stops current, but not 230v voltage

what are the dangers of providing any connection between live wire and earth

creates a short circuit- this triggers a massive surge of current

what is the equation connecting power, potential difference, and current- with units

power = potential difference x current

power in watts

potential difference in volts

current in amps

equation connecting current, power, and resistance- with units

power = current squared x resistance

power in watts

resistance in volts

current in amps

state the equations used for the amount of energy transferred by electrical work- with units

energy transferred = power x time

energy transferred = charge flow x potential difference

energy transferred in Joules

power in Watts

time in seconds

charge flow in coulombs

potential difference in Volts

how does power of a circuit relate to the potential difference across it and current through it

power = voltage x current

describe how the power of a circuit device is related to the energy transferred over a given time

directly proportional

what is the national grid

how electrical power is transferred from power stations to consumers

what do step up transformers do and why?

• increase potential difference- travel a long distance across pylons

• decrease current- reduces thermal energy lost

what do step down transformers do and why?

• decrease potential difference- to be safe for domestic use

• increase current- to actually be at an effective level

what is static charge?

when insulating materials are rubbed against each other, becoming electrically charged

describe the transfer of electrons in static electricity, using charge

negatively charged electrons rubbed off one material onto the other. the material that gains electrons becomes negatively charged and the one that loses electrons becomes positively charged

what happens to the electrically charged objects in static electricity

the opposite charges attract, and like charges repel, both of which are non-contact forces

explain how static electricity can lead to sparking

as charge builds up, a significant potential difference builds up. if charge gets big enough, the air between the objects can no longer act as an insulator, so electrons jump the gap to neutralise charge- electrostatic discharge. this is a spark

how can you tell if an object is charged?

see if it attracts or repels

where is an electric field strongest

closer to the charged object

where is an electric field weakest?

further from the charged object

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

a force is experienced

what is the correlation between distance and force of charged objects

the closer the objects, the larger the force

where do electric field lines run between

from positive, to negative

equation for density, with units

density = mass / volume

density in kg/m cubed

mass in kg

volume in metres cubed

describe particle model in solids, liquids, and gases

• solids- neat rows, all touching. strong intermolecular forces, and all vibrate around a fixed point

• liquid- weaker intermolecular forces, so can flow- all particles touch

• gas- can be compressed- weak forces of attraction between particles- none touch

REQUIRED PRACTICAL 5- DENSITY

REGULAR OBJECTS

• measure lengths with ruler, and mass on a mass balance

• density = mass / volume

• ensure all measurements are in correct unit

IRREGULAR OBJECTS

• find the mass of the object using a mass balance

• fill a eureka can with water

• place the object into the water, and measure the volume of water displaced

• the volume of water displaced = volume of the object

• density = mass / volume

are changes of state chemical or physical changes?

physical

what is sublimation?

solid to a gas with no liquid phase between

what is internal energy?

the energy stored inside a system by the particles- total kinetic and potential energy

what does heating do to the internal energy of a system?

increases internal energy by increasing thermal energy, or results in a change of state

what is the term for the energy needed for a substance to change state?

latent heat

what is latent heat?

the energy needed for a substance to change state

what is specific latent heat

the energy needed to change the state of 1kg of a substance, w no change in temperature

what is the term for the energy needed to change the state of 1kg of a substance, w no change in temperature

specific latent heat

specific latent heat of fusion

solid- liquid

specific latent heat of vaporisation

liquid - vapour

why does increasing temp increase pressure

increasing temp also increases kinetic energy. collide w walls of container faster and more frequently

radius of an atom

1× 10 (-10) metres

what fraction of the radius of the atom is the nucleus

1/ 10000

how might the arrangement of electrons in shells change between energy levels

absorption of electromagnetic radiation- move to higher energy level

emmision of electromagnetic radiation- move to lower energy level

put in order the development of the atom

• JJ Thompsons plum pudding model- positive charge w negative electrons

• alpha scattering experiment- ernest rutherford- nuclear model, mass is concentrated in nucleus

• niels bohr- electrons orbit on shells

• proton discovered

• james chadwick- neutrons in nucleus

how does an unstable nuclei go about becoming stable?

giving out radiation in a random process called radioactive decay

what is activity in radiation? what is it measured in?

the rate at which a source of unstable nuclei decays. it is measured in Becquerels

how is the number of decays per second recorded

count-rate. it is done with a detector like a geiger muller tube

what are the three types of radiation?

alpha, beta, gamma