physics paper 1 revision notes grade 9-1

Topic P1-Energy

Energy stores: kinetic, thermal,chemical,gravitational potential,elastic,electrostatic,magnetic and nuclear

A system is an object or group of objects

calculating energy changes                 

kinetic energy= 0.5 x mass x (speed)2 or ek = 1/2 mv2

gravitational potential energy= msss x gravitational field stength x height or Ep=mgh

elastic potential energy= 0.5 x spring constant x extenstion or Ee=1/2 ke2

specific heat capacity and internal energy

internal energy is the total kinetic and potential energy of all the particles that make up a system

specific heat capicity is the amount of energy needed to raise the temperature of 1kg of a substances by 1 degree

change in thermal energy= mass x specific heat capacity x temperature

power

power(W)= energy transferred (J) divided by time (s) or power = work done divided by time

reducing unwanted energy transfer

lubrication-reduces frictional forces between objects

insulation- reduces the rate of energy transfer by heating. this is used in homes by usung thermal insulations

bio fuels and non renewables

bio fuels- made from animal poo waste and plants

can be used to produce electricty or used to run cars

non-reneweables are reliable but not enough to meet current demand

non-renwables contribute to global warming, make a mess of the landscape, and create acidic rain

energy rescources

renewable rescources: can replenished as quickly as they are being used

example of reneweable rescources: sun, wind, water waves, bio-fuels and tides

non- reneweable rescources: can't be replenished as quickly as they are being used

example of non- renewable rescources: coal, oil and natural gas

energy rescources can be used for transport and for heating

 efficiency

efficiency= useful output energy transfer divided by total input energy transfer or

useful power input divided by the total power input

to increase efficiency off an energy transfer, the amount of wasted energy needs to be reduced

nothing is every 100% efficient, the less energy wasted, more efficent the energy transfer is

Topic P2- electricity

electric current- is the flow of the electrical charge- the greater the flow the higher the current

current is measured in amps (A)

electrical charge is measured in coulombs (C) and can be calculted using this equation:

charge flow= current x time ( Q= It)

resistance and potential difference

the resistance of a component is the measure of how it resists the flow of charge

potential difference= current x resistance ( V= IR)

potential difference is measured in volts (V) using a voltmeter

the higher the resistance:

- the more difficult it is for the charge to flow. The lower the current

resistance is measured in ohms

circuits and resistance

ohmic conductors: a resistor where current is directly proportional to the pd at a constant temperature

thermistors: resistance of a thermissto decreases as the temperature increases. it can be used car engines and centeral heating thermostats

LDR: the resistance of a ldr changes as the intensity of light increases. it can be used in…