E N E R G Y AIMS yAppreciate how energy affects our lives yDescribe the environmental considerations...
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Transcript of E N E R G Y AIMS yAppreciate how energy affects our lives yDescribe the environmental considerations...
E N E R G Y
AIMS
Appreciate how energy affects our lives Describe the environmental considerations
related to energy production Identify renewable energy sources Perform calculations to determine how
much energy is present in a system Produce systems diagrams to show energy
transformations Determine energy efficiency of a system
W H A T I S E N E R G Y ?
Energy is a concept defined as the ability to do work
It is all around us and comes in many different forms
It cannot be destroyed or created but can only be transformed
Machines and living things transform or convert energy
A car converts chemical energy into mechanical energy
A TV converts electrical energy to light energy
F o s s i l F u e l s
Fossil fuels are combustible and hold much energy
Easily stored and transported
Some challenges in retrieving them
Formed over time from decayed/ compressed matter
Consider
Coal and peat Oil and Natural Gas
Coal and Peat
Dead plants rot slowly in a wet environment
Peat is formed in the early stages of decay
Can be cut and burnt as fuel
Over much longer (100’s millions of years) coal can form due to compression of layers above
Mined in various ways
Oil and Natural Gas
Dead animals compressed over time (as coal) became oil
Some decayed more and became natural gas
Gas is cleaned/ purified and pumped directly to users
Crude Oil has many uses but treated first to produce fuels, chemicals (plastics eventually).
Is a valuable resource
N u c l e a r E n e r g y
Uranium ore mined and used to generate power
Needs to be split to release it’s energy (fission)
Same process as a nuclear bomb but controlled in the reactor
Are serious implications with nuclear power Lethal waste products (lethal for a LONG
time)
Safety
Economic sense (short term solution?)
Environmental Issues
Greenhouse Effect Most of world power derived from Fossil Fuels Burning these fuels releases Carbon Dioxide Is believed that a build up in the upper atmosphere will trap the Sun’s
heat and heat up the planet (Greenhouse Effect)
Acid Rain Burning Coal releases sulphur and nitrogen Rainwater falls through these oxides in atmosphere This produces sulphuric and nitric acids Problem as poisons lakes and effects plant and animal growth
Oil Pollution Moved in vast tankers Old vessels are single hulled and when bumped vent their cargo
destroying Eco systems
Conserving resources
Fossil fuels are limited (they will run out)
This type of fuel is known as Non-Renewable or Finite
How can we save energy?
By using more energy efficient systems, such as light bulbs
Renewable Energy Sources
As fossil fuels will run out at some point we need to consider other energy sources.
Energy sources that come from daily sunshine are called renewable sources
These include solar power, wind energy, hydroelectricity and energy from the tides and waves
R e n e w a b l e E n e r g y
SOLAR
In its simplest form a water tank on the roof will heat up and provide hot water
Photovoltaic cells (contain crystals of silicon) convert light energy into electricity
Wind
Modern turbines placed in groups (wind farms) Production depends on wind strength and so
variable Also thought of as ugly on the landscape New idea is to place them in shallows of the
mainland and out of sight
More renewable...
HYDROELECTRIC
A controlled flow of water (head) allowed to flow through a turbine
Generates power
Large scale head produced with a dam
Small scale water tunnel with sluice gate
Tidal
Gravity from Sun/ Moon pulls tide into estuary
Dam/ barrier raised creates a head of water
Released through turbine
Work Done
WORK DONE = FORCE X DISTANCE
Force in Newtons (N) Distance in metres (m) moved in the direction of the force Unit of work is Nm or Joules (J)
A winch raises a lift of mass 1000kg to a height of 20m.Calculate the minimum amount of work done by the winch
Weightlift = mg = 1000 x 9.8 = 9810N
Work Done (winch) = F x D = 9800 x 20 =
196kJ
WORK DONE (Pupil Problems)
Q1. During the loading process, a fork- lift truck lifts a pallet of bricks of mass 740kg up to a height of 2m. Calculate the minimum work done by the truck and suggest a reason why the actual work done will be greater.
Q2. A mass of 50kg is raised to a height of 5m by a rope, which is wound around a pulley on a motor shaft of diameter 150mm as shown. Determine the amount of work done by the motor and the number of revolutions made during the lift.
K i n e t i c E n e r g y
Name given to the energy a body possesses due to its motion
Depends on two things:
the mass (m) of the body (measured in kg) velocity (v) of the body (measured in m/s)
EK = ½ m v2
P o t e n t i a l E n e r g y
Energy stored in a static object
Depends on two things:
the mass (m) of the body (measured in kg) height (h) of the body (measured in m) above a set datum
EP = m g h
E l e c t r i c a l E n e r g y
Name given to the energy produced by power stations via turbines
Depends on three things:
the circuit current (I) measured in Amps voltage (v) of the circuit (measured in Volts) Time that the circuit has been operating (t) measured in
seconds
Ee = I t V
H e a t E n e r g y Energy transferred to a body that results in a
change in the body's temperature
Depends on 3 things:
Mass Specific Heat Capacity
Change in temperature
Eh = m c ΔT
Energy questions
1. When an Olympic diver stands on a diving board 10 m above the pool, what form of energy does he possess?
2. When the diver jumps on the diving board it will bend. What form of energy does the board now possess?
3. When the diver is at the highest point of his dive why does he not have any kinetic energy?
4. The diagram below shows a representation of a hydroelectric power station.
Name the form of energy at each of the stages A, B, C and D
TU R BIN E G EN ER ATO R M O TO R
DAMWATER
A
B C D
Energy questions
1. During a sheet-making process, 50 kg ingots of metal are passed along rollers at a speed of 0.5 m/s. Calculate the kinetic energy of each ingot.
2. A girl of mass 50 kg is riding on her bicycle and has a kinetic energy of 2.5 kJ. What speed is the girl moving at, and what is the kinetic energy of the bicycle if it has a mass of 30 kg?
3. An escalator has six people on it with a total mass of 900 kg. If the escalator moves at a uniform speed of 0.5 m/s, what is the average amount of kinetic energy that each person contains?
Energy questions
4. Baggage handlers at an airport, place suitcases on to a conveyor belt, which lifts them up to the hold of the aeroplane as shown. What is the potential energy of a case of mass 22kg at the top of the conveyor?
5. Metal piles are driven into the ground using a pile driver. The driver is raised to a height of 5 m above the ground and then released.Calculate the weight of the driver if the potential energy stored when it has been lifted is 9810 joules.
3.5m
Energy questions
6. If the amount of electrical energy used by a 110 V, 30 A d.c. motor is 1.98 MJ, for how long has the motor been in operation?
7. Calculate the heat energy required to heat 2 kg of water from a temperature of 20 ºC until it begins to boil.
Energy questions
8. The heating element in a shower can produce heat energy at a rate of 7 kJ/s. Water enters the system at a temperature of 15C and is heated to 40C. Estimate the flow rate (in litres per second) and state any assumptions you have made. (1 litre = 1Kg
57 kJ of thermal energy is supplied to 1.7 kg of oil having a specific heat capacity of 2.7 kJ/kgK. If the initial temperature of the oil is 3C, what will be its final temperature?