Exam Qs

• How can the energy of a system be changed?

  Through the work done by forces which transfer kinetic energy to an object. In electrical equipment which transfer electrical energy to power something, through heating - stored energy is transferred to heat
• Define Power


  The rate of energy transfer(rate of work done) power = work done/time
• What is a watt

  one joule per second
• What is the relationship between kinetic energy and GPE?

  GPE lost = KE gained
• Define Conservation of energy


  energy cannot be created or destroyed, only converted from one form into another
• Describe the changes in the way energy is stored when an object is projected upwards

  Ke -> GPE
• Describe the changes in the way energy is stored when an object hits an obstacle

  KE of moving object -> kinetic energy in the obstacle -> heat + sound energy
• Describe the changes in the way energy is stored when an object is accelerated by a constant force


  source of energy providing the acceleration -> KE in the object
• Describe the changes in the way energy is stored when a vehicle slows down

  KE -> heat energy in the brakes
• Describe the changes in the way energy is stored when water is brought to a boil in an electric kettle

  Electrical energy -> thermal energy in the heating component -> thermal energy in water -> some energy is transformed into sound
• provide examples of non contact forces

  Gravity, magnetism, electrostatic forces
• Provide examples of contact forces

  Normal contact force(upwards force from floor), friction
• Define Centre of mass

  the point where the mass appears to be concentrated
• How do you find the mass of an asymmetric object?

  Suspend card from pivot, attach plumb line, draw vertical line on card where string rests, suspend car from a second point. Where two lines cross = centre of mass
• what is a moment

  a turning effect of a force
• how do you increase the moment of a force

  increase force and distance
• How does a low gear affect speed and turning effect?

  • Low speed
  • High Turning effect
• How does a high gear affect speed and turning effect?

  High Speed

  Low turning effect
• a lever used as a force multiplier exerts a greater force applied to the lever by effort
• The pivot of a force multiplier is nearer to the line of action of the force it exerts than to the force applied to it
• gears are used to change the turning effect
• What is a fuse?

  A wire that melts if the current is too high
• Why are fraying cables dangerous when using mains electricity in the home

  They are a potential electrocution risk
• Why are long cables dangerous when using mains electricity in the home

  tripping hazard
• Why is water dangerous when using mains electricity in the home

  They conduct electricity, so could electrocute you
• Various wires in a plug?

  earth = green and yellow

  brown = live

  blue = neutral
• What is double insulation and why is it used?

  Both the wires inside a device and the outer case of a device is insulated - no chance of electrocution
• Describe the structure of a transformer

  Laminated core made from iron

  2 coils found on opposite sides

  Step up transformers have more turns on the secondary coil than primary

  Step down transformers have less turns on the secondary coil than primary
• Role of a transformer?

  Change the size of alternating voltage

  There are a different amount of turns on the input and output sides
• Difference between step-up transformers and step-down

  Step-up used to step up power station voltages to grid voltage

  step down used to step down the grid voltage to a voltage that can be used safely in homes (230V)
• Energy is transferred between different energy pathways. What are they?

  Mechanical

  Electrical

  Heating

  Radiation
• What is a system?

  An Object or group of objects