Physics- Heat Transfers
Thermal Radiation- All objects emit thermal radiation- The hotter an object is, the more thermal radiation it emits.
Dark matt surfaces emit snd absorb more thermal radiation than light, shiny surfaces.
Conduction- Conduction in a metal is due to free electrons- non metals are poor conductors of metals because they do not have free electrons- good insulators have pockets of trapped air.
Covection-Convection happens when a fluid is heated- the heat makes htem less dense and they rise, ie, hot air rises
Heat loss from buildings can be reduced by cavity wall insulation, double glazing, loft insulation
Forms of energy- Chemical, kinetic, gravitational potential, elastic,elcetrical, sound, light, thermal.....
Energy can chamge from one form to another- energy cannot be created or destroyed.
Useful energy- Energy transferred to where it is wanted in the form it is wanted, eg- rollercoaster- kinetic energy
Wasted energy- Energy that is not useful- eg- rollercoaster- sound and thermal (from friction)
Efficiency= useful energy transferred by a device / total energy transferred by a device- Wasted energy causes inefficiency!
Electrical Energy- Eletrical energy is energy transfer due to an electrical current.
The more powerful a device is, the faster the rate at which it transforms energy.- The unit of power is watts.
The National Grid- is a network of cables and transformers
- We use step up transformers to increase the voltage to the grid voltage - We use step down transformers to decrease the voltage for use in homes
Wind power- turbines are driven by wind which turns a generator- pro- renewable- con- unsightly , unreliable
Hydro electric power- a wave generator is a floating generator turned by waves- pro-renewable, reliable- con- expensive
Solar Power- uses the sun to make power- pro- renewable- con- does not work at night
geothermal- comes from the energy released by radioactive substances deep inside the earth- pro-renewable, no pollution- con-expensive, only certain places have geothermal capabilities
Fossil fuels and nucleasr fuels are non renewable.