Energy Flashcards
What is a system?
An object or group of objects.
What happens when a system changes?
The way that energy is stored changes.
Name the 8 main energy stores
Chemical
Kinetic
Gravitational potential
Elastic
Thermal
Magnetic
Electrostatic
Nuclear
Chemical energy
The energy held in chemical bonds (that connect atoms and molecules together).
Kinetic energy
To do with the motion or movement of an object.
Law of conservation of energy
Energy cannot be created or destroyed, only transferred between different forms and objects.
Gravitational potential energy
The energy that an object possesses because of its position in a gravitational field.
Thermal (internal) energy
The heat energy trapped within an object, related to temp of that object.
Elastic energy
The energy held in an already-stretched spring.
Magnetic energy
Energy associated with a magnetic field.
Nuclear energy
Energy gained from breaking atoms apart.
In what ways can energy be transferred?
Mechanically
Electrically
By heating
By radiations (light/sound waves)
What is the change in the way energy is stored when an object is projected (thrown) upwards?
The kinetic store decreases and the gravitational potential energy store increases.
What is the change in the way energy is stored when a moving object hits an obstacle?
Kinetic energy can be transferred and energy can be dissipated as sound and thermal energy.
What is the change in the way energy is stored when an object accelerates at a constant speed?
The kinetic energy store of the object will increase when it’s accelerated by a force.
What is the change in the way energy is stored when a vehicle slows down/breaks?
The kinetic store decreases and the thermal energy store increases due to friction in the brakes.
What is the change in the way energy is stored when water is brought to the boil in an electric kettle?
Energy is transferred electrically to increase the thermal store in the water.
What is a closed system?
An isolated system where no energy flows in and out of the system.
The kinetic energy of a moving object can be calculated using what
equation?
Ek = 1/2 m v²
what is the unit for energy?
joules, J
what is the unit for mass, m ?
kg
what is the unit for speed, v ?
m/s
The amount of elastic potential energy stored in a stretched spring
can be calculated using what equation?
Ee = 1/2 k e²
What must we assume when calculating the amount of elastic potential energy stored in a stretched spring?
That the limit of proportionality has not been exceeded.
What is the unit for extension, e?
metres (m)
The amount of gravitational potential energy gained by an object
raised above ground level can be calculated using what equation?
Ep = m g h
What is the unit for gravitational field strength, g ?
N/kg
The amount of energy stored in or released from a system as its
temperature changes can be calculated using what equation?
∆ E = m c ∆ θ
What is the symbol for change in thermal energy?
∆ E
What is the symbol for specific heat capacity?
c
What is the unit for specific heat capacity?
J/kg °C (joules per kilogram per degree Celsius)
What is the symbol for temperature change?
∆θ
What is the unit for temperature change?
°C
What is specific heat capacity?
The amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius.
Power definition
The rate at which energy is transferred or
The rate at which work is done.
What are the two key power equations?
P = E/t
P=W/t
What is the symbol for work done?
W
What is the unit for work done?
J (joules)
What is the unit for power, P ?
W (watts)
What is the symbol for energy transferred?
E
What is the unit for energy transferred?
J (joules)
What do we measure time in?
Seconds.
An energy transfer of 1 joule per second is equal to what?
A power of 1 watt.
A power of one watt is equal to what?
An energy transfer of 1 joule per second.