E N E R G Y

1. 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

2. 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

3. Where does energy come from? • Energy in the food we eat comes from the sun

4. 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

5. 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

6. 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

7. 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?)

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. Wave WAVE •  Bobbing ducks generate power via turbines • Strung out in long lines either off or on shore

15. Tidal • Gravity from Sun/ Moon pulls tide into estuary • Dam/ barrier raised creates a head of water • Released through turbine

16. E n e r g y C a l c u l a t i o n s

17. 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

18. 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.

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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?

25. 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.

26. 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.

27. 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?