Sources of Energy

Ms. Angel’s 3rd Grade

Greenbriar West Elementary

2004-2005

Teaching Strategy• Lecture

– Reinforce terms from handout provided by GBW

– Interactive – use handout as framework, not many answers on the sheets

– marks the sheets the students will get

• Lab– Provide handout for lab groups to use

– Reinforce skills in observation, data collecting, data plotting, and making conclusions

Topics

• Energy– Mass and Force– Potential and Kinetic Energy– Electricity

• Renewable Energy Sources

• Nonrenewable Energy Sources

Energy

Examine mass, force, and work as an introduction to energy and power

Mass

• What is mass?

• Does a party balloon have more mass than a candy bar?

• How do you figure out an object’s mass?

Mass

• What is mass?– Matter or stuff

• Does a party balloon have more mass than a candy bar?– Bring in one of each; contrast size vs mass

• How do you figure out an object’s mass?– Weigh it; but is mass the same thing as weight? No,

will talk about this in a moment; mass of something is the same no matter what but its weight varies…

Force – Key Points

• What is a force?

• Why does gravity exert a force on you?

• If an object is not moving does that mean that there are no forces on it?

Force – Key Points Answers

• What is a force?– Something that pushes or pulls you

• Why does gravity exert a force on you?– Two objects with mass attract each other

• If an object is not moving does that mean that there are no forces on it?– It may but it probably means that the forces

acting on an object cancel out

ForcesThe man is standing still.Are there any forceson the man?

If so, draw them.

floor

ForcesThe force due to gravityis the same in size,but opposite indirection, to the forceby the floor!!!!

Floor

Gravity

Gravitational Force - Questions

• So what causes a gravitational force?

• Is there a gravitational force on the moon?– Is it larger or smaller than the gravitational

force on the Earth?

Gravitational Force - Answer

• So what causes a gravitational force?– Two objects are attracted to each other

Object 2 (has mass)

Object 1 (has mass)

F1

F2

F1 = F2

Gravitational Force

• Gravitational force keeps us “stuck” to the Earth!!!• We actually pull on the Earth but the Earth is too big to move!!!

Earth

Person

F

F

Fperson = FearthHow much you weigh depends on your mass and the mass of the planet you are on.

Gravitational Force - Questions

• Is there a gravitational force on a person standing on the moon?– Is it larger or smaller than the gravitational

force on the Earth?

– Why?

Gravitational Force -Answers

• Is there a gravitational force on the moon?– Is it larger or smaller than the gravitational

force on the Earth? yes• The gravitational force is smaller on the moon – 1/6

of the Earth.

– Why?• The moon is smaller (1/6th the mass) than the Earth.

How the Moon Causes Tides

• Since the water in the oceans are liquid they are pulled out of shape by the moon’s gravitational force– Causes water level to rise thus creating tides (i.e. water

seemingly getting deeper and shallower for no apparent reason)

Earth Moon

Water bulging up

Weight vs Mass• Weight is a force: W = m g

– m = mass and – g = acceleration due to gravity = 9.81 m/s2

m (kg) W (N)

10 98

5 49

12 118

5 52

18 177

5 47

8 78

Mass, kg

Wei

ght,

N

0 2 4 6 8 10 12 14 16 18 20

40

020

6080

100120140160180

PLOT THE DATA!!

Weight vs Mass• The slope of the plot is g = 9.81 m/s2

m (kg) W (N)

10 98

5 49

12 118

5 52

18 177

5 47

8 78

Mass, kg

Wei

ght,

N

0 2 4 6 8 10 12 14 16 18 20

40

020

6080

100120140160180

X

X

X

X

X

X

X

Break

Work

• Review: Force is a push or a pull

• Exerting a force over a distance is WORK

– For example, pushing the desk across the room is “a lot of work”

Potential and Kinetic Energy – Key Facts

• What is energy?

• What is potential energy?

• What is kinetic energy?

Potential and Kinetic Energy – Key Facts

• What is energy?– Ability to do work

• Potential energy – “stored” energy– How can we “store” energy?

• Kinetic energy – energy of movement– How is potential energy converted into kinetic energy?

Potential Energy

Does the ballhave any storedenergy here?

Does the ballhave any storedenergy here?

Potential Energy

Does the ballhave any storedenergy here?

Does the ballhave any storedenergy here?

NOYES, we moved the ballagainst gravity (did work)

Potential Energy

What happens when we let goof the ball?

If the ball is to move show the direction of the ball.

Label the forces on the ball!!!!

Potential/Kinetic EnergyWhat happens when we let goof the ball?

It starts to fall – has kinetic energyConvert potential into kinetic energy

If the ball is to move show the direction of the ball.

Label the forces on the ball!!!!Gravity is larger force than air resistance

velocity

Gravity

Air resistance

Quick Review of Science Facts

• Force is a push or pull

• Work is exerting a force over a distance

• Energy is the ability to do work

• Power is energy being used over a period of time

Introduction to Electricity

Electricity

• Electricity is a form of energy that starts with  atoms. – Atoms are too small to see, but they make up everything around us.

– An atom has three tiny parts:  protons,  neutrons, and  electrons. The center of the atom has at least one proton and one neutron. At least one electron travels around the center of the atom at great speed.

• Electricity is created by forcing electrons to flow from atom to atom. – What kind of energy is this?

Electricity - Answers

• Electricity is a form of energy that starts with  atoms. – Atoms are too small to see, but they make up everything around us.

– An atom has three tiny parts:  protons,  neutrons, and  electrons. The center of the atom has at least one proton and one neutron. At least one electron travels around the center of the atom at great speed.

• Electricity is created by forcing electrons to flow from atom to atom. – What kind of energy is this?

Kinetic energy – the electrons are moving

How Electricity is Generated

• Most electricity used in the United States is produced at  power plants. – Various energy sources are

used to turn  turbines. – The spinning turbine shafts

turn electromagnets that are surrounded by heavy coils of copper wire inside generators.

– This creates a magnetic field, which causes the electrons in the copper wire to move from atom to atom.

Nonrenewable Energy Sources

Renewable vs Non-Renewable?

• What is a renewable energy source?

• What is a non-renewable energy source?

Renewable vs Non-Renewable?

• What is a renewable energy source?

– You can make more of it

• What is a non-renewable energy source?

– There is a limited amount of it and you cannot make more of it

Break

Non-Renewable Energy Sources

• Give some examples of nonrenewable energy sources

Fossil Fuels• The majority of electricity used in the United States

is generated from power plants that burn fossil fuels (coal, oil, and natural gas).– Why do we call these fossil fuels?

– Why does this make them nonrenewable?

• When the fossil fuels are burned they heat water and make steam. – The highly pressurized steam is directed at the blades of turbines to make them

spin.– What type of energy conversion is this process?

Fossil Fuels• The majority of electricity used in the United States

is generated from power plants that burn fossil fuels (coal, oil, and natural gas).

– Why do we call these fossil fuels?

• Oil, coal, and gas are formed by many tiny organisms being compressed (high heat and pressure) by layers of sand and rock over the years

– Why does this make them nonrenewable?

• It takes millions of years to create fossil fuels

• When the fossil fuels are burned they heat water and make steam. – The highly pressurized steam is directed at the blades of turbines to make them spin.– What type of energy conversion is this process?

• Potential into kinetic and kinetic into kinetic

Nuclear Energy• Nuclear power plants use the

heat from splitting atoms to convert water into the steam that turns turbines. – These plants rely on uranium, a

type of metal that must be mined from the ground and specially processed.

– Fuel rods containing uranium are placed next to each other in a machine called a nuclear reactor.

– The reactor causes the uranium atoms to split and in so doing, they release a tremendous amount of heat.

Renewable Energy Sources

Renewable Energy Sources

• Give some examples of renewable energy sources – be creative!!!

Solar Energy

• Solar energy is generated without a turbine or electromagnet. Special panels of photovoltaic cells capture light from the sun and convert it directly into electricity. The electricity is stored in a battery.

• What type of energy conversion process is happening here?

Solar Energy

• Solar energy is generated without a turbine or electromagnet. Special panels of photovoltaic cells capture light from the sun and convert it directly into electricity. The electricity is stored in a battery.

• What type of energy conversion process is happening here?

– Kinetic to electrical

Wood

• Burn wood from trees to produce heat to create steam by heating water which in turn power turbines

• Wood is renewable only if trees are replanted and grown as quickly as they are used

• Why is wood not normally used to make electricity?

Wood• Burn wood from trees to

produce heat to create steam by heating water which in turn power turbines

• Wood is renewable only if trees are replanted and grown as quickly as they are used

• Why is word not used to make electricity?

Doesn’t create much heat (per lb) and is very messy

Grain Fuel - Ethanol

• Distill grain into a liquid fuel called ethanol that can be used for cars and power plants– Renewable source is simply

grain (e.g. wheat, barley, etc – like those used in bread) – can always grow more

– Over 2 million cars per year in the USA already are set up to run on E85 (85% ethanol and 15% gasoline)

Geothermal Power

• Steam (or hot water converted to steam) from under the ground is used to turn turbines.– Usually from geysers or hot

springs

• Why might this form of energy not be used very much?

Geothermal Power

• Steam (or hot water converted to steam) from under the ground is used to turn turbines.– Usually from geysers or hot springs

• Why might this form of energy not be used very much?

Not many hot springs and difficult to pipe steam or hot water

Hydropower• Hydroelectric plants use the power

of falling water to turn the turbines that help generate electricity. Water stored behind a dam is released and directed through special tubes to flow against the blades of turbines and make them turn. – What type of energy conversion is

taking place?

• Hydropower provides about 10 percent of the electricity generated in the United States. – The most famous hydroelectric facility

in the country is Hoover Dam.

Wind Power• Wind is usually created by uneven

heating of the earth• The force of the wind is used to

spin many small turbines. • Most wind power is produced from

wind farms — large groups of turbines located in consistently windy locations.

• Why might wind power be difficult to generate?

Wind Power• Wind is usually created by uneven

heating of the earth• The force of the wind is used to spin

many small turbines. • Most wind power is produced from

wind farms — large groups of turbines located in consistently windy locations.

• Why might wind power be difficult to generate?

Some days it is not windy and the windmills or turbines take up a lot of room

Wind and water power experiment(split class into two teams)

Water• Pour a gallon of water

each day into hydropower plant

• Count turns of the wheel

• Plot the data• Reuse water• Make observations

Wind• Take wind power plant

outside each day for one hour

• Count turns of the gear• Plot the data• Make observations

Wind and Water Plots

Day

1 2 3 4 5 6 7 8 9 10

Turns

10

8

6

4

2

0

Use W for wind and H for water (hydro)

Wind and Water Plots(possible example results)

Day

1 2 3 4 5 6 7 8 9 10

Turns

10

8

6

4

2

0

Use W for wind and H for water (hydro)

W

W W

W

W

W

W

W WW

H

H HH

H

H HH

H

H

Experiment Summary

• What would be the best way to produce energy – water or wind?

Energy Source Good About It Bad About It

Water

Wind

Ms Angel’s Class

Experiment, Plot, ObserveAnd Conclude