Topic 1: Energy Flashcards
What are the eight forms of energy?
Thermal, Kinetic, Gravitational Potential, Elastic Potential, Chemical, Magnetic, Electrostatic, Nuclear.
What is the calculation for Work Done?
WORK DONE = FORCE x DISTANCE
W = F x D
Joules = Newtons x Metres
Define Work Done.
Work done is the product of the force and the distance over which the force is applied.
What is the calculation for Weight?
WEIGHT = MASS x GRAVITATIONAL FIELD STRENGTH W = m x g Newtons = Kilograms x Newtons per Kilogram
What is the calculation for Gravitational Potential Energy (GPE)?
GRAVITATIONAL POTENTIAL ENERGY = MASS x GRAVITATIONAL FIELD STRENGTH x HEIGHT
Ep = m x g x h
Joules = Kilograms x Newtons per Kilogram x Metres
What is the calculation for Elastic Potential Energy?
ELASTIC POTENTIAL ENERGY = 1/2 x SPRING CONSTANT x (EXTENSION)^2
Ee = 1/2k x e^2
Joules = Newtons per Metre x Metres^2
What is the calculation for Kinetic Energy?
KINETIC ENERGY = 1/2 x MASS x (SPEED)^2
Ek = 1/2m x (v)^2
Joules = Kilograms x Metres per Second^2
What is the calculation for Efficiency?
EFFICIENCY = USEFUL ENERGY TRANSFERRED
———————————————–
TOTAL ENERGY SUPPLIED
Can an energy transfer be more than 100% efficient?
No, no energy transfer can be more than 100% efficient.§
Why do machines waste energy?
Machines waste energy because of friction between their moving parts, air resistance, electrical resistance, and noise.
What is the equation for power?
POWER = WORK DONE
———————
TIME
Watts = Joules / Seconds
What is another equation for power?
POWER = ENERGY TRANSFERRED
————————————
TIME
Watts = Joules / Seconds
One Watt =?
One Watt = 1 joule of energy transferred per second.
What is the Conservation of Energy Principle?
Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed.
Define Power
Power is the rate of energy transfer or the rate of doing work.
Define a powerful machine
A powerful machine is one which transfers a lot of energy over a short amount of time.
Define Conduction
Conduction is the process where vibrating particles transfer energy to neighboring particles. It occurs mainly in solid.
Define Convection
Convection is where energetic particles move away from hotter to cooler regions.
How is energy transferred?
Energy can be transferred mechanically, electrically, by heating or by radiation
For a falling object with no air resistance?
Energy lost from the g.p.e. store = Energy gained in the kinetic energy store
Equation linking energy transferred to s.h.c.?
Change in thermal energy = mass x s.h.c. x change in temperature
J = kg x J/kgoC x oC
How to investigate s.h.c?
Measure the mass of a block and then wrap it in insulating materials to reduce energy transferred from the block to the surroundings.
Insert thermometer and heater. Measure initial temperature and set the p.d. of the power supply to 10v.
As the block heats up, take readings if the temperature and current every minute for 10mins.
Turn off the heater and use P = VI to calculate power.
Then use E = Pt to calculate how much energy has been transferred to the heater.
Plot the graph and find the gradient to work out the s.h.c. through: 1/(gradient x mass of the block)
Ways of reducing unwanted energy transfers?
Have thick walls
Use thermal insulation
Cavity wall insulation
Loft insulation
Double-glazed windows
Draught excluders around doors and windowsNon-renewable energy resources?
Coal Oil Natural Gas They will all run out one day They all damage the environment But they provide most of our energy
Renewable energy resources?
The sun Wind Waves Tidal Bio-fuel Tides Geothermal Hydro-electric They will never run out Some can be unreliable
Wind Power?
Through putting up wind turbines in exposed places
The wind turns the blades, which turns the generator and produces energy
No pollution
Can be noisy
Some say they spoil the scenery
Initial costs are high but no fuel costs and minimal running costs
No permanent damage to the landscape
You cannot increase the power output when faced with increased demand
Solar power?
Solar cells generate electric currents directly from sunlight
No pollution
In sunny countries, very reliable but only in the daytime
Initial costs are high but energy is free and little to no running costs
small-scale energy output
Geothermal power?
In volcanic areas where hot rocks are near the surface
Source is the slow decay of various radioactive elements
Free energy that’s reliable and with very little damage to the environment
Not many suitable locations
Hydro-electric power?
usually requires the flooding of a valley by building a dam
Water is allowed steadily out which powers turbines
No pollution
Big environmental impact
and possible loss of habitat for some species
it can provide immediate responses to an increased demand for energy.
Initial costs are high but no fuel costs and minimal running costs
Wave power?
Lots of small wave powered turbines located around the coast
No pollution
But seabed is disturbed and the habitats of marine animal can be destroyed
Fairly unreliable and when the wind drops, waves die out
Initial costs are high but no fuel costs and minimal running costs
Tidal power?
By building a tidal barrage that is a dam built across river estuaries with turbines in them
As the tide comes in, it fills up the estuary and the water is then allowed out through the turbines at a controlled speed.
Tides produced by the gravitational pull of the sun and moon
No pollution
Prevents free access by boats, spoiling the view and altering the wildlife’s habitat.
Initial costs are moderately high but no fuel costs and minimal running costs
Bio-fuels?
From either plant products or animal dung
and can be burnt to produce electricity or run cars in the same way as fossil fuels.
Supposedly carbon neutral
Fairly reliable, as crops take a relatively short time to grow, but they cannot respond to immediate energy demands
The cost to refine biofuels is very high
Non-renewable power?
fossil fuels and nuclear energy are reliable. There’s currently enough to meet current demands and are extracted from the earth at a fast enough rate that the power plants can always have fuel in stock
But they are slowly running out
The setup costs of a power plant can be quite high, the running costs aren’t that expensive and it is cost effective.
They produce CO2 into the atmosphere, adding to the greenhouse effect and contributing to global warming.
Coal and oil can also release sulfur dioxide which causes acid rain
Coal mining spoils the landscape
Oil spillages can cause serious environmental problems
Nuclear power is clean but the waste is dangerous and difficult to dispose of and carries the risk of major catastrophe.
