Energy Resources and Transfers Flashcards
There are 8 main stores of energy.
State 4 of these main energy stores.
-Chemical
-Kinetic
-Gravitational
-Elastic
-Thermal
-Magnetic
-Electrostatic
-Nuclear
What is meant by the “conservation of energy”?
● Energy cannot be made or destroyed but can change from one form to another (for example GPE to KE).
● The total amount of energy in a closed system remains constant
What are the four main transfer types between energy stores?
-Mechanically (by force)
-Electrically (includes current flow)
-By heating (conduction,convection,radiation)
-By radiation (light and sound)
How can energy be transferred through electrical equipment?
Energy is stored as chemical in the battery. Then current converts chemical energy into other forms electrically.
How can energy be changed through work done by forces?
A force converts energy mechanically by work done. E.g If a moving objects is travelling upwards, its kinetic energy is converted to GPE by work done against its weight(force)
A skateboarder starts at rest at the top of a hill, she pushes herself down a rough hill and comes to rest at the bottom. What energy changes take place?
● She starts with GPE and does work to push herself down the hill.
● As she is riding down, GPE turns into KE and friction.
● Eventually all of the energy is lost through heating the surroundings through the friction between the ground. There is no KE and she is at rest.
State an equation that is used to calculate “efficiency” of a system
What energy changes are involved when a moving car stops?
Kinetic energy changes to heat energy (through friction) and sound energy
What changes are involved when a ball (initially stationary) rolls down a hill?
● GPE turns into KE as it rolls downwards
● The speed will increase as the vertical height decreases
What is wasted energy?
● The energy that is not used by the device for its desired purpose is the waste energy.
● An example is a kettle: when energy is changed to sound energy it is classed as waste energy since it is not being used to heat the water
In what ways thermal energy can be transferred?
- Conduction
- Convection
- Radiation
Explain why electrical heater of a kettle is placed at the bottom
Heat is mainly transferred by convection within fluids. When a part of the liquid is heated, it expands and becomes less dense therefore it rises up within the fluid. Colder part of the liquid is now denser so it sinks down within the liquid and this forms a convection current when heater is placed at the bottom.
How does the thickness of a building’s walls affect the rate of cooling?
The thicker the building walls are the further heat has to travel to escape, hence as you increase the thickness you decrease the rate of cooling.
How does the thermal conductivity of a building’s walls affect the rate of cooling?
The higher the thermal conductivity the easier it is for heat to escape, hence as you increase the thermal conductivity, you also increase the rate of cooling. Metals have high thermal conductivity so they are conductors. Air has lower thermal conductivity so air is an insulator.
Explain how surfaces can be adjusted for heat transfer by radiation
If an object is hotter than the environment it emits, if it’s colder it absorbs thermal radiation. Black, dull surfaces are good emitters/absorbers but bad reflectors of thermal radiation White, shiny surfaces are bad emitters/absorbers but good reflectors of thermal radiation
What equation is used to measure the work done on an object?
What is the relationship between work done on an object and energy transferred to the object?
What equation is used to calculate the change in gravitational potential energy?
What equation is used to calculate kinetic energy?
State an equation linking work done, power and time taken for an appliance
