Energy

Energy

1. Non-renewable

   • The main energy resources available for use on Earth include: fossil fuels (coal, oil and gas),

2. Renewable

   • List of renewable energy sources  - Hydroelectric. - Wind  - Solar  - Tidal  - Wave  - Geothermal  - Biomass 
   • do not release green house gases into the atmosphere
     • nuclear fuel, bio-fuel, wind, hydroelectricity, geothermal, the tides, the Sun and water waves.
   • Are not running out - unlike coal which is in high demand and low supply

3. Changes in energy

   • kinetic energy = 0.5 × mass × speed2 (the speed is squared
     • elastic potential energy = 0.5 × spring constant × extension 2
   • g . p . e . = mass × gravitational field strength × height
   • Lots of important equations here!
   • change in thermal energy = mass × specific heat capacity × tempperature change ∆ E = m c ∆ θ
     • Required practical activity 1: investigation to determine the specific heat capacity of one or more materials. The investigation will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored.

4. Energy stores and transfers in systems

   • There are changes in the way energy is stored when the system changes
     • For an example, when an object is projected upwards, kinetic energy is transferred to kinetic energy, then to gravitation potential energy and then to kinetic energy until it becomes stationary
       • When an object falls freely, its potential energy gets converted into kinetic energy. When the object hits the ground, its kinetic energy gets converted into heat energy and sound energy.
         • An object accelerated by a constant force: Work is done by a force on an object. This work is converted to the object's kinetic store
           • A kettle will transfer the supplied electrical energy to both useful and wasted energy stores. The useful energy store will heat the water and the wasted energy stores will be dissipated to the surroundings.
       • A vehicle slowing down: To begin with, the vehicle's energy is in the kinetic store. The brakes do work slowing the car down. During this process, energy is dissipated (lost) through heat and sound. A moving object hitting an obstacle: The object's energy is in the kinetic store at the start because it is moving.

5. Power

   • Power = energy/time

6. Conservation and dissipation of energy

   • Efficiency
     • Efficiency = useful total energy transfer/total energy transfer
   • The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.

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