Energy Work And Power Flashcards
Energy transfers and stores
Energy transfers, when energy transfers between different forms because of an event/process
- heating eg:conduction convection
- waves
- electrical current eg: power source to a bulb
- mechanical working , eg:collision
Energy stores
- gravitational
- potential
- elastic
- chemical
- nuclear
- thermal
- electrostatic
- magnetic
What is energy
Energy is a property that must be transferred to an object in order to perform work on or heat up that object
It is measured in units of Joules (J)
The principle of conservation of energy
Energy cannot be created or destroyed, it can only be transferred from one store to another
This means that for a closed system, the total amount of energy is constant
Kinetic energy
Formula: 1/2 mv^2 =EK
EK, kinetic energy measured in joules
M, mass in kg
V, speed of the object (velocity) (m/s)
Meaning: The energy an object has as a result of its mass and speed
Gravitational potential energy
Meaning: The energy an object has due to its height in a gravitational field
If an object is lifted up, energy will be transferred to its gravitational store
If an object falls, energy will be transferred away from its gravitational store
Formula: mgh= EP
M= mass (kg)
G=gravitational field strength (10N on earth)
H= change in height in metres
EP= gravitational potential energy (joule)
The energy transformation that takes place when a ball falls to the ground
When the ball is at the maximum height, the GPE is at max and KE is zero
When the ball is falling, the GPE is turning into KE
When the ball hits the ground, the GPE is at zero and the KE is at max, and most of the remaining energy is dissipated into the ground as heat and sound energy (this can’t be converted)
What is work done
Electrical and mechanical work done is the amount of energy transfers between stores
Work done = force x change in distance (displacement)
How can useful energy/electrical energy be obtained
Fossil fuels
Water (hydroelectric, waves, tidal)
Geothermal
Nuclear
Solar
Wind
Biofuels
Advantages and disadvantages to renewables and non renewables
Non renewables
- larger energy output
- usually cheaper
- very harmful for the environment
- more reliable than renewables (but one day run out)
Renewable
- often more costly
- less reliable
- not harmful to the environment
- doesn’t run out ever
- produced at a smaller scale
Electricity generation by fossil fuels
- Boiler (furnace) burns materials, when the coal is burned it produces thermal energy
- This thermal energy is used to boil water creating steam to turn a turbine
- The turbine turns coils in a magnetic field in the generator, generating energy
- By using a step up transformer it is carried out of the system to houses by electrical lines
How does the sun get energy
By nuclear fission and scientist are still researching on how to do nuclear fission to create energy at a large scale
Efficiency equation
Useful energy/power output / total energy/power input x 100% = efficiency
What is the concept of efficiency
What is power
The rate of this energy transfer, or the rate of work done
(The rate of doing work)
Power equations
Power is the rate of doing work
P = w/t
P=power
W= work done
T= time
P = E/T
E= energy transferred
Power is measured in watts
