Topic 3 Conservation Of Energy Flashcards
What are the main eight energy stores?
Chemical- fuel
Kinetic- moving objects
Gravitational potential- raised mass
Elastic- stretched spring
Thermal- hot object
Magnetic- two magnets
Electrostatic- two charges
Nuclear- radioactive decay
What is a closed system?
A closed system is one where energy can flow in or out of the system, but there is no transfer of mass. An example of a closed system is a pan of water being heated that has a lid on it so that no steam can escape.
What are the energy transfers?
Energy is transferred from one store to another in four different ways:
Mechanically- by a force moving through a distance
Electrically- by the use of electric current
Thermally- because of a difference in temperature
Radiation- by waves such as electromagnetic or sound
What is Thermal energy transfer?
The rate which thermal energy is transferred through a wall of a house depends on:
- the difference in temperature between the warmer interior and the colder exterior
- the thickness of the walls
- the material that the walls are made from
What is efficiency?
All machines waste some of the energy they transfer. Most machines waste energy as heat energy. The Efficiency of a machine is a way of saying how good it is at transferring energy into useful forms.
The equation for efficiency= useful energy transferred by the machine/ total energy supplied to the machine x 100%
What are the energy resources?
The main energy resources include both renewable and non-renewable resources.
Renewable energy sources:
- bio-fuels= animal or plant matter
- hydroelectricity= water flowing in a dam
- wind turbines= use the wind
- tidal power= tide power
- solar cells= energy from the sun
Non-renewable energy resources:
- nuclear fuels= uranium
- fossil fuels= coal, oil and natural gas
What are the patterns in energy use?
In the world the most used energy source is fossil fuels. Whereas in 1900, biomass in the form of wood was the major source of fuel and its use has remained constant over time. In more recent years, there has been an increase in the use of nuclear fuel and hydroelectric power.
What is potential and kinetic energy?
Gravitational potential is the energy possessed by a body due to its height above the earth.
The value of the gravitational potential energy stored depends on:
- the mass of the body
- the height the body is raised
- the gravitational field strength
The equation for gravitational potential energy is:
Change in gravitational potential energy= mass x gravitational field strength x change in vertical height
The gravitational field strength on earth is 10N/Kg
Kinetic energy is stored in moving objects and is calculated using the equation:
Kinetic energy= 1/2 x mass x speed(squared)
What is conservation of energy?
Energy cannot be created or destroyed only transferred
Why are mechanical processes bad?
Mechanical processes become wasteful when they cause a rise in temperature so dissipating energy in heating the surroundings
