P1

• what is a system?

  an object or a group of objects
• most important thing about energy?

  energy is never created or destroyed, only transferred between different forms and objects
• what are the 8 energy stores?

  1. thermal
  2. electrostatic
  3. chemical
  4. gpe
  5. magnetic
  6. elastic
  7. nuclear
  8. kinetic
• energy can be transferred ?

  • heating
  • electrically
  • mechanically
  • radiation
  • sound
• if you have a kettle and you fill it up with water, when you turn it on, electrical energy from the plug socket flows to the heating element of the kettle where its transferred electrically to the thermal energy store which means the flow of electricity warms the metal heating element. The heating element then transfers the energy to the waters thermal energy store.
• another way of saying energy transferred is?


  work done
• 2 main types of work done?

  • mechanical
  • electrical
• mechanical work done involves?


  using a force to move an object
• electrical work done involves?


  when current flows
• a train is about to cross a broken bridge, in order to stop, it applies the brakes which creates friction between the brakes and wheels. So the friction does work as it slows the train down because it causes energy in the wheel's kinetic energy stores to be transferred to the thermal energy store of the surroundings in the form of heat which will slow down the train.
• kinetic energy = 0.5 × mass × (speed) squared

  • kinetic energy= joules
  • mass= kg
  • speed= m/s
• what is kinetic energy?

  the energy stored in moving objects
• stationary objects have no kinetic energy
• elastic potential energy= 0.5 ×  spring constant × (extension) squared

  • epe= joules
  • spring contstant= n/m
  • extension squared= m
• when we stretch a spring, were applying a force to change the length of the spring. Applying a force like this is called doing 'work'. We're putting energy in to stretch the spring. The stretched spring is storing this energy and we call that energy elastic potential energy.
• the extension of the spring is directly proportional to the force applied
• if we apply to much force, then the extension is no longer directly proportional to the force. At this point, the spring has been stretched beyond the limit of proportionality.
• gpe = mass × gravitational field strength × height

  • gpe= joules
  • mass= kg
  • gravitational field strength= n/kg
  • height= m
• what is gpe ?


  is the energy stored in an object due to its position above the earths surfaces. This is due to the force of gravity acting on an object .
• gravitational field strength?


  9.8 or rounded to 10
• weight = mass x gravitational field strength
• The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation:

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

  mass= kg

  specific heat capacity= j/kg

  temperature change- celsius
• The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.
• required practical 1 ?

  determine the specific heat capacity of a material
• what is the method of the practical specific heat capacity?

  1. measure and record the mass of the copper block
  2. place a heater into the larger hole in the block
  3. place the thermometer in the smaller hole
  4. wrap the block in an insulating layer to reduce the energy transferred from the block to the surroundings
  5. measure the initial temperature of the block and set the potential difference of the power supply to 10V.
  6. turn on the power supply and start a stopwatch
  7. as the block heats up, take readings of the temperature and current every minute for 10 min.
• whats step 8 of specific heat capacity?

  1. turn power supply off and calculate the power supplied to the heater (P=VI)
  2. use this to calculate how much energy has been transferred to the heater at the time of each temperature reading using the formula (E=Pt)
  3. plot a graph, find gradient, SHC of the material of the block is 1/ (gradient x mass of the block)
• Power is defined as the rate at which energy is transferred or the rate at which work is done.
• power = energy transferred / time

  power = work done / time

  • power - watts
  • energy transferred - joules
  • time - seconds
  • work done - joules
• An energy transfer of 1 joule per second is equal to a power of 1 watt.
• Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.
• for blenders and fans, the electrical energy is transferred to the kinetic energy of electric motors and thats because the main purpose of both of these appliances is movement, the blender moves to mix the food and the fan moves to create air currents. There will also be a small amount of thermal energy produced due to friction in the motors.
• a kettle and iron both use electrical energy from the mains but they transferred into thermal energy because these appliances are designed to get hot. Neither of these appliances create kinetic energy.
• You can divide appliances in to 2 categories?

  those that transfer electric energy into kinetic energy, and those that transfer electrical energy into thermal energy. Some appliances do both.
• A hair dryer and a washing machine both use electrical energy and both of them transfer to kinetic and thermal energy.
• A motor moves air through the hair dryer and the heating element heats the air.
• in the washing machine, the heating element heats the water and a motor turns the drum to wash the clothes.
• appliances which are designed to generate thermal energy usually have high power rating than appliances which are designed to generate kinetic energy.
• current (amps) is measured using an ammeter
• The energy efficiency for any energy transfer can be calculated using the equation: efficiency = useful output energy transfer / total input energy transfer
• Efficiency may also be calculated using the equation:

  efficiency = useful power output / total power input