Energy Flashcards
What are the energy stores and examples
- magnetic (compasses, fridge magnets)
- internal or thermal (body, stoves)
- chemical (foods, muscles)
- kinetic (runners, buses)
- electrostatic (thunderclouds) - elastic potential (inflated balloons, compressed springs)
- gravitational potential (kites, mugs on table)
- nuclear (nuclear reactors, uranian nuclear power)
What are the types of energy transfer and what are they
- mechanical work (force moving an object through a distance)
- electrical work (charges moving due to p.d)
- heating (due to temp diff caused electrically or by chemical reaction)
- radiation (energy transferred as a wave like light and infrared which are emitted from sun)
What is dissipation
- often used to describe ways in which energy is wasted
- lost to the surroundings
What is an example of dissipation
- electrical cables
- not useful to have hot wires behind a tv as energy is dissipated to surrounding air
How is energy dissipated in a mechanical system
- when two surfaces rub together (work is done against friction which causes heating of the two surfaces)
- adding lubricant can reduce this friction so that less heat is wasted
how can energy dissipation be reduced in an electrical context
- LED bulbs as opposed to filament lamps causes less energy to be wasted
How is energy usually lost
- By heating up the surroundings
- can be dissipated as sound waves
Conservation of energy
- energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed
What is the equation for calculating kinetic energy
kinetic energy (j) = 1/2 x mass (kg) x speed (m/s) squared OR Ek = 1/2mv squared
Elastic potential energy equation
elastic potential energy = 1/2 x spring constant (n/m) x extension (m) squared
OR
Ee = k e squared
How many centimetres in a metre
100cm
Gravitational potential energy equation
Gravitational potential energy = mass (kg) x gravitational field strength (N/kg) x height (m)
OR
Ep = m g h
What is the gravitational field strength always
10 N/kg
What are the major energy resources available to produce electricity
- fossil fuels
- bio- fuel
- hydroelectricity
- geothermal
- tidal
- water waves
- the sun
What does burning fossil fuels do
- releases co which adds to the greenhouse effect
- releases sulphur dioxide which causes acid rain
