4.1-4.17 Flashcards
Energy stores and transfers
Energy is either stored in a certain way or is being transfered. It can not be anything other than than stored or transfered
Chemical (energy stores)
The energy stored associated with chemicals bond, such as those between molecules(food, muscles, electrical cells)
kinetic (energy stores)
The energy associated with a moving object (Runners, busses, comets)
Gravitational (energy stores)
The energy associated with an object at a height (aeroplanes, kites, mugs on a table)
Elastic (energy stores)
The energy stored when an object is streched, squashed or twisted (Drawn catapullts, compresed springs, inflated balloons)
Thermal (energy stores)
In most cases this is the vibrations of the particles in the object. In the hotter objects, the particles vibrates faster (The human bodies, hoy coffees, kettle
Magnetic (energy stores)
The energy stored when like poles are pushed closer together or when unlike poles are pulled further apart (fridge magnets, compasses and magnet trains which use levitation)
Electrostatic (energy stores)
The energy stored when like charges are moved closer together or when unlike charges are pulled further appart (Thunderclouds, Von de Graaff
Nuclear (energy stores)
The energy associated with nuclear interactions (Nuclear fusion of hydrogen and helium in the sun, Uranium - 245 undergoing fission)
mechanically (energy transfers)
A force moving an object through through a distance
Electrically (energy transfers)
Charges moving due to a potential difference
by heating (energy transfers)
Due to temperature difference
by radiation (energy transfers)
energy tranferred as a wave e.g. light, sound and infrared radiation
Conservation of energy
Energy can not be destroyed or created, so it is always stored or transfered. This means that energy is regularly transfered from one store to another, although sometimes it is considered to be ‘wasted’ when it is transferred to a store that is not useful
The efficiency of an energy conversion system is defined as:
efficiency = useful energy output/ total energy output x 100%
Conduction
Transfer of heat in solids through the vibration of particles (always from hot to cold)
Convection
Transfer of heat through fluids (liquids and gases) by the upward movement of warmer less dense areas of fluid
Radiation
Transfer of energy by infrared (IR) waves
Infrared radiation does not need matter or particles to transmit energy, instead it is able to travel through a vacuum. E.g. from the sun to earth through space
emission (radiation)
An object that is hotter then its surroundings emits infrared radiation. Hotter objects emit radiation faster than cooler objects.
absorption (radiation)
An object that is colder than its surroundings absorb infrared radiation
work done equation:
work done = force x distance moved (W = F x D)
work done is equal to….
energy transferred
gravitational potential energy
gravitational potential energy = mass x gravitational field strength (10) x height
GPE = M x G x H
kinetic energy equation
kinetic energy = 1/2 x mass x speed²
KE = 1/2 x M x V²
power equation
power = work done / time taken
Insulation
Foam in wall cavity
Carpets trap air
Layer of roof insulation
Double glazing
Using draught excluders
Blocking unused chimneys
Type of energy stores
- Chemical
- Kinetic
- Gravitational
- Elastic
- Thermal
- Magnetic
- Electrostatic
- Nuclear
Type of energy transfers
- Mechanically
- Electrically
- By heating
- By radiation
