energy stores & transfer

• Energy:

  The ability to do work, it follows the principle of CONSERVATION OF ENERGY.

  • Measured in Joules (J)
• Energy can be stored in different ways:

  • THERMAL ENERGY
  • CHEMICAL ENERGY
  • KINETIC ENERGY
  • ELASTIC POTENTIAL ENERGY
  • NUCLEAR ENERGY
  • MAGNETIC ENERGY
  • ELECTROSTATIC ENERGY
• THERMAL / internal ENERGY:

  The heat energy trapped within an object.

  • Related to the temperature of that object.
  • The HOTTER an object, the MORE energy in its thermal energy stores.

  
• CHEMICAL ENERGY:


  Held in chemical bonds, releases energy due to a CHEMICAL REACTION.

  • Found in food, batteries & fuels.

  
• KINETIC ENERGY:


  Energy of the movement or motion of an object.

  
• GRAVITATIONAL POTENTIAL ENERGY:


  The energy stored due to an object's position in a GRAVITATIONAL FIELD.

  
• ELASTIC POTENTIAL ENERGY:


  The energy held in an already-stretched spring.

  • Stored when objects are STRETCHED or SQUASHED.

  
• NUCLEAR ENERGY:


  Energy from breaking atoms apart, released during nuclear reactions.

  
• MAGNETIC ENERGY:


  Due to the attraction or repulsion between MAGNETS.

  
• ELECTROSTATIC ENERGY:


  Due to the attraction or repulsion between CHARGED PARTICLES.

  
• Energy Transfers:


  Energy can move between these stores through different pathways. 
• The different energy transfer pathways:

  • Mechanical work
  • Heating
  • electric work
  • Radiation like: light or sound wave

  
• MECHANICAL WORK:


  When FORCE is applied, like:

  • pushing a box
  • Physically stretching an elastic band

  
• HEATING:


  Transfer of energy from a HOT object to a COLD object, like a kettle heating water.

  
• ELECTRIC WORK:


  When current flows in a circuit and transfers energy like:

  • an electric fan
  • plugging something into a socket

  
• RADIATION:


  When energy is transferred in the form of a WAVE like:

  • Light or sound waves
  • The Sun warming the Earth.

  
• A Person Throwing a Ball Upwards:

  • The energy in the CHEMICAL energy store of the person from their food is transferred MECHANICALLY.
  • Because a force is applied to the ball to the KINETIC energy store of the ball.
  • As the ball rises, it slows down because the energy in its kinetic energy store is being transferred MECHANICALLY to its gravitational potential energy store.
  • Because the object is getting higher.

  
• A Kettle Boiling Water:

  Initially, the heating element in the kettle is HOT & the water is COLD.

  • Energy is transferred from the THERMAL energy store of the heating element.
  • By HEATING to the thermal energy store of the water, causing it to get hotter.

  
• A Car Accelerating with a Constant Force:

  • The energy in the CHEMICAL energy store of the car from the petrol in it reacts in the engine.
  • It transfers energy MECHANICALLY to the KINETIC energy store of the car.

  
• A Car Braking:


  Friction between the brakes & wheels causes WORK to be done.

  • Causing energy in the KINETIC energy store to be transferred mechanically to the thermal energy store of the surroundings, like the road & the air.

  
• A Car Crashing:


  If a car was to crash into a wall, most of the energy from its kinetic energy store is transferred mechanically to the thermal energy store of the wall.

  • As there's a force acting on it from the car.

  
• Whenever energy is transferred to an object, the energy is stored in one of that object’s energy stores.
• When a system changes, energy is transferred either between objects or between different forms.
• When you burn fuel, energy is transferred from the fuel's chemical energy store to the thermal energy store of the surroundings.

  
• When you throw a ball up in the air, it moves through a gravitational field.

  • It slows down as it rises, because energy from it's kinetic energy store is being transferred to its gravitational potential energy store.
• Energy is transferred to a light bulb electrically.

  • Energy transferred away from a light bulb by heating & light.
• As an object falls, energy is transferred from its gravitational potential energy store, to its kinetic energy store.
• When a kettle filled with water is turned on:

  • electrical energy from the plug socket, flows to the heating element of the kettle.
  • It's transferred electrically to the thermal energy store of the kettle’s heating element.
  • Meaning the flow of electricity warms the metal heating element.
  • The heating element then, transfers the energy over to the water’s thermal energy store.
• Another way of saying energy transferred is work done.

  Types of work done:

  • mechanical
  • electrical

  
• Mechanical work done:


  Involves using a force to move an object.

  
• Example of mechanical work done:

  Kicking a ball up in the air, involves energy from the chemical energy store of your leg, being transferred to the kinetic energy store of the ball.

  
• Electrical work done:


  When current flows, the energy required to overcome the resistance in the wires of a circuit.
• A train that’s about to stop:

  • It applies the brakes, creating friction between the brakes & the wheels.
  • 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 stores of the surroundings in the form of heat.
  • which will hopefully slow down the train.

  
• Examples of close systems:

  • A thermos flask that keeps your drink hot or cold – it's closed because it doesn't allow heat to escape or enter.
  • The energy stored in a battery is stored in its chemical energy store.
• In a burning candle, chemical energy store is converted into thermal & light energy store.
• The total energy of the racing track and the car is constant.

  
• Child:

  • Gravitational potential energy decreases
  • Kinetic energy increases and then decreases to zero

  Springs:

  • Elastic potential energy increases

  Surroundings:

  • Internal store of energy increases

  
• • The chemical store of energy of the wood decreases.
  • The internal store of energy of the pipe and water increases.

  
• • As height changes, gravitational potential energy changes.
  • gravitational potential energy decreases, when moving to the lower bar.
  • As speed changes, kinetic energy changes
  • kinetic energy increases when moving to the lower bar
  • transfer from gravitational potential energy to kinetic energy as height decreases.
  • the sum of the kinetic energy & gravitational potential energy is constant.

  
• As the aeroplane moves upwards through the air, there's a decrease in the kinetic energy of the aeroplane.