energy resources and energy transfers

• kinetic energy is anything moving
• thermal energy is any object, the hotter it is the more energy it has
• chemical energy is anything that can release energy by a chemical reaction
• gravitational potential energy is anything in a gravitational field
• elastic potential energy is anything stretched
• electrostatic energy is two charges that attract or repel each other
• magnetic energy is two magnets that attract or repel each other
• nuclear energy is where atomic nuclei release energy from this store in nuclear reactions
• energy can be transferred between stores in four main ways : mechanically where an object is moving due to a force acting on it :electrically where a charge moving through a potential difference:by heating where energy is transferred from a hotter object to a colder object : by radiation where energy is transferred (light or sound waves)
• energy can be stored transferred between stores and dissipated but it can never be created or destroyed. the total energy of a closed system has no net change
• a closed system is just a system that can be treated completely on its own without any matter being exchanged with the surroundings
• energy is only useful when it is transferred from one store to a useful store
• some of the input energy is always lost or wasted often to thermal energy stores by heating
• total energy input = useful energy output +wasted energy
• the less energy wasted the more efficient the device is
• Another way of describing a Watt is 1 joule per second (J/s)
• The equation used to calculate the power of a device is: power = work done / time
• The thickness of a building's walls affects the rate of cooling - thicker walls result in a slower rate of cooling as heat has to travel a greater distance to escape.
• Thermal energy can be transferred through conduction, convection, and radiation.
• The electrical heater of a kettle is placed at the bottom to create a convection current within the liquid, where heated liquid rises and colder liquid sinks.
• Surfaces can be adjusted for heat transfer by radiation - objects that are hotter than the environment emit thermal radiation, while objects that are colder absorb thermal radiation.
• The thermal conductivity of a building's walls affects the rate of cooling - higher thermal conductivity allows heat to escape more easily, resulting in a faster rate of cooling.
• The equation used to calculate the efficiency of a system is Efficiency = Useful energy output / Total energy input
• The equation used to calculate kinetic energy is KE = ½mv² (kinetic energy (joule, J) = ½ × mass (kilogram, kg) × (speed)² ((m/s)²)).
• In physics, "power" refers to the rate at which energy is transferred.
• White, shiny surfaces are bad emitters/absorbers but good reflectors of thermal radiation.
• To reduce unwanted heat transfer, methods include insulation in walls and ceilings, double glazed windows, and the use of curtains to prevent heat loss by radiation.
• Black, dull surfaces are good emitters/absorbers but bad reflectors of thermal radiation.
• The equation used to measure the work done on an object is Work Done = Energy Transferred.
• thermal radiation is the transfer of energy by heating by inferred electromagnetic waves
• conduction is the main form of energy transfer by heating in solids
• convection is the main form of energy transfer by heating in liquids and gases
• all objects are continually emitting and absorbing infrared radiation
• an object that’s hotter than it’s surroundings emits more radiation that it absorbs
• an object that’s cooler than it’s surroundings absorbs more radiation than it emits
• thermal conduction is the process where vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of neighbouring particles
• convection occurs when the more energetic particles move from the hotter region to the cooler region
• convection is most efficient in roundish or squarish containers because they allow the convection currents to work best
• convection currents are all about the changes in density
• materials with a high thermal conductivity transfer energy between their particles quickly