Topic 3 - Conservation of energy Flashcards
Heat transfers
What happens when an object is heated?
Energy is transferred to its thermal energy store (temperature increases)
Heat transfers
How is heat transferred in solids?
Through conduction:
vibrating particles transfer energy to neighbouring particles
Heat transfers
What happens to the particles in a metal when they are heated
Energy is transferred to the metal in the kinetic energy store (vibrations)
Heat transfers
Why can conduction only occur in solids?
Particles in a solid are held together very densely meaning there are a lot of collisions to pass on energy
Heat transfers
What is thermal conductivity
It is how well objects transfer energy by conduction.
- Metals have high conductivity (transfer heat energy quickly)
- Plastics have low thermal conductivity (used as insulators)
Heat transfers
Where does convection take place and how does it work?
Takes place in gases and liquids. When fluids are heated, particles gain kinetic energy and move around, diffusion means that low pressure energetic particles will move to colder area
Heat Tranfers
How do you stop convection?
You need to stop the freeflow of fluids
Heat transfers
What do conduction and convection have in common
Both involve particles gaining kinetic energy
Heat Transfers
How can thermal energy be transferred without particles?
Energy can be transferred via radiation (infrared waves). The hotter the object is the more infrared radiation it emits.
Insulation
What is an insulator?
A material that is a poor conductor of heat e.g. wool
Insulation
How do you keep a house warm in a cold envrionment?
Reduce the amount of thermal energy the escapes to the surroudnings. This can be done by:
* Ensuring a proper seal to ensure air cannot escape
* Reducing heat lost by conduction (heat through solids) by building thick walls composed of low thermally conductive materials or using cavity walls (walls with air gaps in between as to minimise conduction) and is filled with insulating foam to prevent convection.
* Double-glazed windows - 2 panes of glass with air gap to minimise heat loss by conduction.
Energy transfers
Explain and name the ways energy can be transferred
- Mechanically - A force acts upon an object e.g. pushing or stretching
- Electrically - A charge doing work e.g charge moving around a circuit
- Heating - Energy tranferred from hotter to colder objects
- Radiation - Energy transferred by waves e.g. energy from the sun reching earth by light
Energy transfers
What is conservation of energy
Energy cannot be created or destroyed. Total energy of a closed system does not change.
Energy transfers
What is useful energy?
Energy that was used for its purpose e.g. light emitted by a light bulb
Energy transfers
What is wasted energy?
Energy not used for its intended purpose and is lost to the surroundings e.g. heat given off by a light bulb
Energy transfers
Name the 8 energy stores
- Thermal - heat
- Kinetic - Movement
- Gravitational potential - Anything in a gravitational field
- Elastic potential - Stretched/Compressed
- Chemical - Reaction
- Magnetic - 2 attracting poles pulled apart or 2 repelling poles pushed together
- Electrostatic - 2 attracting charges pulled apart or 2 repelling charges pushed together
- Nuclear - Energy stored within the nucleus of an atom
Energy tranfers
Explain kinetic energy
Anything that is moving, increases when speed increases, decreases when speed decreases (depends on mass and speed)
KE (J) = m (kg) * v squared (m/s) / 2
Energy transfers
Explain gravitational potential
Lifting an object in a gravitational field causes a transfer of energy to the GPE store of the raised object the higher it is - the more energy stored
Change in GPE (J) = mass (kg) * gravitational field strength (N/kg) * change in vertical height (m)
