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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

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e n e r g y
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
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
where does energy come from
Where does energy come from?
  • Energy in the food we eat comes from the sun
f o s s i l f u e l s
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
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
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
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
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
    • Some are old and run by dodgey Greek tycoons
    • Old vessels are single hulled and when bumped vent their cargo destroying Eco systems
conserving resources
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
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
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
slide12
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
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
slide14
Wave

WAVE

  •  Bobbing ducks generate power via turbines
  • Strung out in long lines either off or on shore
tidal
Tidal
  • Gravity from Sun/ Moon pulls tide into estuary
  • Dam/ barrier raised creates a head of water
  • Released through turbine
work done
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 9.81 = 9810N

Work Done (winch) = F x D = 9810 x 20 = 196.2KJ

work done pupil problems
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
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
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
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
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
Energy questions
  • When an Olympic diver stands on a diving board 10 m above the pool, what form of energy does he possess?
  • When the diver jumps on the diving board it will bend. What form of energy does the board now possess?
  • When the diver is at the highest point of his dive why does he not have any kinetic energy?
  • 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

energy questions1
Energy questions
  • 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.
  • 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?
  • 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 questions2
Energy questions
  • 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?
  • 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.
energy questions3
Energy questions
  • 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?
  • Calculate the heat energy required to heat 2 kg of water from a temperature of 20 ºC until it begins to boil.
energy questions4
Energy questions
  • 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 15C and is heated to 40C. Estimate the flow rate (in litres per second) and state any assumptions you have made.
  • 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 3C, what will be its final temperature?