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
WHAT IS ENERGY?
 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?
 Energy in the food we eat comes from the sun
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
Nuclear Energy
 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
Renewable Energy
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
Wave
WAVE
 Bobbing ducks generate power via turbines
 Strung out in long lines either off or on shore
Tidal
 Gravity from Sun/ Moon pulls tide into estuary
 Dam/ barrier raised creates a head of water
 Released through turbine
E n e r g y
C a l c u l a t i o n s
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.
Kinetic Energy
 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
Potential Energy
 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
Electrical Energy
 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
Heat
Energy
 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.
2.
3.
4.
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.
A
DAM
WATER
B
C
D
TURBINE
GENERATOR
MOTOR
Name the form of energy at each of the stages A, B, C and 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
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
4.
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 15C and is
heated to 40C. Estimate the flow rate (in litres per second) and
state any assumptions you have made. (1 litre = 1Kg
Burny
Burny

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?