Physics

• Half Life

  -average time taken for half of a nuclei to decay
• Alpha radiation

  -strong ionising power

  -stopped by paper/skin

  -2 neutrons and 2 protons

  -from nucleus
• Beta Radiation

  -reasonable ionising power

  -stopped by aluminium

  -high speed electron

  -from nucleus as neutron becomes proton
• Gamma radiation 


  -poor ionising power

  -mostly stopped by lead

  -electromagnetic radiation

  -from nucleus
• Nuclear Decay and Radiation

  -atomic nuclei that are unstable give out radiation to become more stable

  -random process
• Isotopes

  -atoms of the same element with the same number of protons but a different number of neutrons
• change in state

  -at the melting or boiling point, adding heat with cause a change in state

  -it is reversible
• Latent heat of fusion

  -energy needed for a substance to melt
• Latent heat of vaporisation

  -energy needed for a substance to evaporate
• Series and parallel circuits

  -voltmeters go in parallel

  -ammeters go in series

  -in a series circuit, the power supply of voltage is shared;

  Vtotal=V1+V2

  12=8+V2

  V2=12-8=4

  V2=4
• internal energy

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

  -doing work increases the energy stored in a system
• specific heat capacity

  -amount of energy required to raise the temperature of 1kg of a substance by 1 degree
• Energy stores

  -Kinetic

  -Chemical

  -Thermal

  -Electrostatic

  -Magnetic

  -Elastic potential

  -Gravitational potential

  -Nuclear
• diodes

  -current will only flow in one direction

  
• Resistors

  -ohmic conductors

  
• Filament Lamp

  -as the current increases, the temp increases

  
• Resistance and Potential Difference

  -resistance of a measure of how component resists the flow of charge

  -PD tells us the difference in electrical potential from one point in a circuit to another
• Electric charge and current

  -Electric current is the flow of electrical charge; the greater the rate of flow, the higher the current
• LED

  -light emitting diode

  
• Thermistor

  -resistance decreases as the temp increases

  -used in fire alarms

  
• LDR

  -Light dependent resistor

  
• Variable resistor

  -Adjusts the value of current or voltage

  
• Energy stores and systems

  -when a system changes, there are changes in how energy is stored
• kinetic energy


  -energy due to motion
• Elastic Potential energy


  -Energy stored when something is stretched or compressed
• Gravitational Potential Energy

  -Energy stored in an object due to its position in a gravitational field

  -the higher the object, the greater the GPE
• Power

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

  $E \div t$
• Reducing power waste

  -lubrication; oil in motor reduces friction so less energy is lost

  -thermal insulation; double glazing, less useful thermal energy is lost
• Thermal conductivity

  -the higher the TC, the easier heat is allowed to travel through the material, so higher rate of energy transfer by conduction across the material
• Efficiency

  -can be increased by;

  reducing waste output (lubrication, thermal insulation)

  recycling waster output (absorbing thermal water and recycling it as input)
• Renewable energy

  -biofuel,solar,tidal,wind

  -can be replenished

  -not always reliable; weather and time of day (solar)

  -visual pollution

  -expensive
• Non-renewable energy

  -Fossil fuels, nuclear fuel

  -finite

  -harmful emissions

  -involve destroying landscapes

  -produce lots of energy for less resource