Unit 1, energy Flashcards
What is the formula for kinetic energy
1/2 x mass x speed2
What is the formula for GPE
Mass x gravitational field strength x height
What is the formula for power
Power = work done/time taken = energy transferred/time taken
What are the formulas for efficiency
Efficiency = useful energy output/ total energy input
Efficiency = useful power output/total power output
What is the formula for elastic potential energy
Elastic potential energy = 0.5 x spring constant x (extension)2
What is the formula for change in thermal energy
Change in thermal energy = mass x specific heat capacity x temperature change
What is the unit for energy
Joules
What is the unit for mass
Kilograms
What is the unit for speed
Metres per second
State the principle of conservation of energy
Energy cannot be created or destroyed but only transferred from one store to another
What is the unit for gravitational field strength
Newtons per kilogram
What is the unit for power
Watts
What is the unit for specific heat capacity
J/kg*c
Unit for spring constant
N/m
What is the definition for power
Power is the rate of transfer of energy or the rate of doing work
What is the unit for work done
Joules
List 8 energy stores
chemical, kinetic, gravitational potential, elastic potential, nuclear, magnetic, electrostatic, thermal
Energy stored in objects which move is…
Kinetic energy
How can you reduce unwanted energy loss in a machine with moving/touching parts?
Use oil/lubricant
A battery is a store of __________ energy.
chemical
Food is a store of __________ energy.
chemical
What can you do to increase a particular object’s kinetic energy store?
Move it faster
What can you do to increase a particular object’s gravitational potential energy store?
Lift it higher
A rock at the top of a hill is a store of ___________ energy.
Gravitational potential
A compressed spring is a store of ___________ energy
elastic potential
Metals are good thermal conductors because they have…
Delocalised electrons
Thermal energy is transferred along a metal object by…
conduction
T or F: A high thermal conductivity means there is a high rate of energy transfer
T
What is “dissipation” of energy
When it spreads out into the surroundings (e.g. by radiation)
T or F: Thicker walls make a house cool down quicker
F
What is a thermal insulator?
A material that does not conduct and which reduces thermal energy transfers.
State 3 ways thermal energy loss from a house can be reduced?
double/triple glazing, loft insulation, cavity wall insulation, draught excluders
Define specific heat capacity
The energy needed to raise the temperature of 1 kg of a material by 1°C
What colour surface emits the most thermal radiation?
(matt) black
What colour surface emits very little thermal radiation?
white/silver
What colour surface absorbs very little thermal radiation?
white/silver
What colour surface absorbs the most thermal radiation?
(matt) black
What is a negative effect of sulphur dioxide, produced when burning fossil fuels?
Acid rain
Examples of non-renewable energy resources
Fossil fuels (coal/oil/natural gas), nuclear fuel
What are advantages of fossil fuels as an energy resource?
reliable, cheap
What is a negative effect of CO2 produced when burning fossil fuels?
Greenhouse gas/global warming
What are disadvantages of fossil fuels?
carbon dioxide (greenhouse gas) produced leading to global warming. Can produce sulphur dioxide causing
What are advantages of nuclear fuel?
No carbon dioxide produced, reliable.
What are disadvantages of nuclear fuel?
nuclear waste remains radioactive for thousands of years. Expensive to build and decommission
Examples of renewable energy resources.
biofuel, wind, hydroelectricity, geothermal, tidal, wave, solar.
What are two advantages of biofuels?
“carbon neutral”, renewable, reliable
What are advantages of wind power?
No carbon dioxide produced, renewable
What are disadvantages of biofuels?
production of fuel can damage ecosystems and reduce variety of crops grown
What are disadvantages of wind power?
unreliable (not always windy), expensive to construct
What are advantages of hydroelectricity?
No carbon dioxide produced; can be used to meet sudden changes in demand
What are disadvantages of hydroelectricty?
need to flood a river valley, blocks rivers preventing fish migration, unreliable during droughts
What are advantages of geothermal energy?
doesn’t damage ecosystems, reliable.
What are disadvantages of geothermal energy?
contain greenhouse gases such as CO2 and methane.These contribute
What are advantages of tidal energy?
What are advantages of tidal energy?
What are disadvantages of tidal energy?
tides vary, may damage tidal ecosystem, need to build a tidal barrage
What are advantages of wave power?
No carbon dioxide produced, renewable
What are disadvantages of wave power?
unreliable - may not produce electricity when calm seas
What are advantages of solar power?
No carbon dioxide produced, renewable, good for remote locations
What are some disadvantages of solar power?
unreliable - no electricity produced at night and limited on cloudy days. Expensive to construct.
What type of energy resource generates electricity from fission reactions?
nuclear energy
What type of energy resouces allows water to be pumped uphill at quiet times, ready for use another
Hydroelectric
What type of energy resource harnesses thermal energy from below the Earth’s surface?
Geothermal
Define “non-renewable”
An energy resource that will run out
Define “renewable”
An energy resource that will NOT run out
All objects emit what type of radiation?
Infrared
What is blackbody radiation?
radiation across a range of wavelengths emitted by an object that absorbs all the radiation incident
Does a hot object emit more or less infrared than a cooler object?
more
What happens to the peak wavelength of blackbody radiation as you increase temperature?
Wavelength decreases
What happens to temperature of an object if it absorbs more IR radiation than it emits?
temperature increases
What happens to the temperature of an object if it emits more IR radiation than it absorbs?
Temperature decreases
