Energy Dissipiation + SHC + Power Flashcards
Specific heat capacity
The amount of energy stored or released from system as its temperature changes can be calculated by knowing SHC
SHC is a property that tells us how much heat energy in joules is needed to raise the temperature of 1kg of a substance by 1 degree Celsius.
Power
Power is the rate at which energy is being transferred or work is being done
Pooerr - watts, time in seconds
One watt is the power from an energy transfer of one joule per second
If both lift same weight to same height, the one that does it faster has a higher power - transfers energy at faster rate
Conservation of energy
Cannot be destroyed of created, only transferred between different energy stores.
Energy dissipation
Not all energy transfers are useful. Dissipation - refers ro the energy that is wasted or not usefully employed by a device.
Example of dissipation
In a phone- energy moves from the chemical energy store of the battery electrically to the kinetic energy store of the phones motor to vibrate.
Phone gets warm - chemical store electrically to thermal energy store of the phone. - not useful and wastes energy.
Why is it important to reduce unwanted energy transfers?
To maximize efficiency and minimize costs.
ESP heat in houses.
How does thermal conductivity help house reduce energy loss?
Thick walls with low thermal conductivity - better at keeping heat inside for insulation. Thin walls, high TC, building will cool down quickly because heat escape faster.
What else can reduce heat loss in houses?
Houses can be constructed with 2 separate walls and an air gap between them, reducing energy transfer by conduction as air has a low conductivity. Filling air gap with insulation foam - low conductivity - increases effect even more.
What are ways to reduce heat loss in a home
Cavity walls
Loft insulation
Double glazing windows
Drought excluders
How does loft insulation reduce heat loss
It’s made from materials with low TC, low insulation reduces energy loss through both conduction and convention. Convection - occurs when liquids and gasses r able to move and transfer heat.
Double glazing windows
Two layers of glass with trapped gas between them - these windows lessen energy loss due to conduction and convection
Drought excluders
Placed around doors and windows, designed to prevent hot air from escaping - reducing convection losses.
How does minimizing frictional forces reduced unwanted energy transfers?
Eg bicycle - when riding chain moves over sprockets.
Causes friction between the links and sprockets. Friction convert some to kinetic energy, bike does forwards, into thermal energy. Not being used as intended and is therefore wasted.
How can u combat the frictional forces?
Lubricate the chain with oil. Lubrication reduces friction and allows for a smoother movement of the chain over the sprockets. More kinetic energy used, ride is more efficient.
