Doğukan Ayberk Paç

Fırat Çanak

Chapter 14 Energy Story

Chapter OutlinePart 1

• Energy– What is energy?– How do we measure energy?– Changing Energy– Forms of Energy

• Heat• Conduction• Convection• Radiation

• Electricity– What is Electricity– Where does it come from?– How does it work?– Resistance & Static Electricity

Part 2•Circuits•Electric Motors•Stored Energy & Batteries

–Definition of Stored Energy–How does the battery works?–Different Types of Batteries–Another method of storing energy

What is energy?

‘ENERGY IS THE ABILITY TO DO WORK’

• Energy can be found in a number of such different forms as– chemical energy– electrical energy– heat (thermal) energy– light (radiant) energy– mechanical energy– nuclear energy

• Energy makes everything happen and can be divided into two types:

– Moving energy : Kinetic energy.• When you push a pencil from the edge of the desk, the moving pencil uses kinetic

energy– Stored energy: Potential energy

• when you pick up the pencil and put it back on the desk, you use your own energy to lift and move the pencil. Moving it higher than the floor adds energy to it. As it rests on the desk, the pencil has potential energy. The higher it is, the further it could fall. That means the pencil has more potential energy.

Btu (British thermal unit)

• Btu is the amount of heat energy it takes to raise the temperature of one pound of water by one degree Fahrenheit, at sea level.

• Example:– One thousand Btus roughly equals one average candy bar.– It takes about 2,000 Btus to make a pot of coffee.

Joules (named after scientist James Prescott Joule)

• One joule is the amount of energy needed to lift something weighing one pound to a height of nine inches.

• 1,000 joules=1 kilojoule=1 Btu• Example

– a piece of buttered toast contains about 315 kilojoules (315,000 joules) of energy. – With that energy you could:

• Jog for 6 minutes• Bicycle for 10 minutes• Walk briskly for 15 minutes• Sleep for 1-1/2 hours

How Do We Measure Energy?

Around the world, scientists measure energy in joules rather than Btus.

Changing Energy

Features• Energy cannot be created or destroyed.

• Energy can be transformed into another kind of energy.

• Energy has always existed in one form or another.

Example:•Stored energy in a flashlight’s batteries becomes light energy when the flashlight is turned on.•Food is stored energy. It is stored as a chemical with potential energy. When your body uses the stored energy to do work, it becomes kinetic energy.•A television changed electrical energy into light and sound energy.

Heat Energy

• Heat is a form of energy that is used for a lot of things, like warming our homes and cooking our food.

• Heat energy moves in three ways:

Heat Energy

Conduction Convection Radiation

Conduction

• Conduction occurs when energy is passed directly from one item to another.

• Example:

– If you stirred a pan of soup on the stove with a metal spoon, the spoon will heat up. – The heat is being conducted from the hot area of he soup to the colder area of the

spoon.– Metals are excellent conductors of heat energy.– Woods or plastics are “bad” conductors (called insulators)– That is why a pan is usually made of metal while its handle is made of a strong plastic.

Convection

• Example:

– The wind we feel outside is often the result of convection currents.

– You can understand this by the winds you feel near an ocean. Warm air is lighter than cold air and so it rises. During the daytime, cool air over water moves to replace the air rising up as the land warms the air over it.

– During the night time, the directions change – the surface of the water is sometimes warmer and the land is cooler.

Convection is the movement of gasses or liquids from a cooler spot to a warmer spot.

Radiation

• The sun’s light and heat cannot reach us by conduction or convection because space is almost completely empty.

• The sun’s rays travel in straight lines called heat rays. When it moves that way, its called radiation.

• When sunlight hits the earth, its radiation is absorbed or reflected. Darker surfaces absorb more of the radiation and lighter surfaces reflect the radiation..

What is Electricity?

• Electricity lights up our homes, cooks our food, powers our computers, television sets, and other electronic devices. Electricity from batteries keeps our cars running and makes our flashlights shine in the dark.

What is Electricity?

• All matter is made up of atoms, and atoms are made up of smaller particles such as the proton, the neutron and the electron.

• Electrons spin around the center, or nucleus, of atoms

• The nucleus is made up of neutrons and protons.

• Electrons contain a negative charge, protons a positive charge. Neutrons are neutral.

• Each atom has a specific number of electrons, protons and neutrons.

• The number of electrons usually needs to be the same as the number of protons. If the numbers are same, the atom is called balanced, and it is very stable.

To begin with…

What is Electricity?

• An atom that gains electrons has more negative particles and is negatively charge. A “charged” atom is called an “ion”.

• Electrons can be made to move from one atom to another. When those electrons move between the atoms, a current of electricity is created.

• The electrons move from one atom to another is a “flow”. One electron is attached and another electron is lost.

• When you add up the electrons and protons, you would wind up with one more proton instead of being balanced.

• Since all atoms want to be balanced, the atom that has been “unbalanced” will look for a free electron to fill the place of the missing one. We say that this unbalanced atom has a “positive charge” (+) because it has too many protons.

• While the free electrons moves around waiting for an unbalanced atom to give it a home. The free electron charge is negative, and has no proton to balance it out, so we say it has a “negative charge” (-).

What is Electricity?

So what do positive and negative charges have to do with electricity?

• Positive atoms and electrons have strong attraction to each other to balanced out.

• The more positive atoms or negative electrons you have, the stronger the attraction for the other. Since we have both positive and negative charged groups attracted to each other, we call the total attraction “charge”.

• When electrons move among the atoms of matter, a current of electricity is created. This is what happens in a piece of wire.

Resistance• Electricity “flows” or moves through some things better than others do because these

materials have some loosely held electrons, which move through them very easily.These are called “conductors”.

– Copper – Aluminium– Steel

• The measurement of how well something conducts electricity is called its resistance.

• Resistance in wire depends on how thick and how long it is, and what it’s made of. The thickness of wire is called its gauge. The smaller the gauge, the bigger the wire.

• A piece of metal can be made to act like a heater. When an electrical current occurs, the resistance causes friction and the friction causes heat.The higher the resistance, the hotter it can get.

• Some things conduct electricity very poorly. These are called insulators. – Rubber (used to cover wires in an electric cord)– Glass (at the end of a power line, there are glass insulators. They keep the metal of

the wires from touching the metal of the towers)

Static Electricity

• Example:

http://www.youtube.com/watch?v=vo1SVOXTfjw

http://www.youtube.com/watch?v=Jm3rHONOr9o&feature=related

•Definition: Electric charge that has accumulated on an object

•Unlike current electricity that moves, static electricity stays in one place.

Static Electricity

Outline of the videos

Baloon • The negative charges in the single balloon are attracted to the positive charges in the

ball.• Negative charges always repel negative charges and positive always repel negative

charges. So the two balloons with negative charges would “push” each other apart.

Lighting• Clouds become negatively charged as ice crystals inside the clouds rub against each

other. Meanwhile, on the ground, the positive charge increases. The clouds gets so highly charged that the electrons jump from the ground to the cloud, or from one cloud to another cloud.

• This causes a huge spark of static electricity in the sky that we call lightning.

Circuits

• Electrons with a negative charge, cannot “jump” through the air to a positively charged atom. They have to wait until there is a link or bridge between the negative area and the positive area. We usually call this bridge a “circuit”.

• When a bridge is created, the electrons begin to move quickly. Depending on the resistance of the material making up the bridge, they try to get across as fast as they can. If you’re not careful, too many electrons can go across at one time and destroy the “bridge” or the circuit, in the process.

• We can limit the number of electrons crossing over the “circuit”, by letting only a certain number through at a time. And we can make electricity do something for us while they are on their way.

Circuits

• For example, we can “make” the electrons “heat” a filament in a bulb, causing it to glow and give off light.

• When we limit the number of electrons that can cross over our circuit, we say we are giving it “resistance”. We “resist” letting all the electrons through. This works like a tollbooth on a freeway bridge. Copper wire is just one type of bridge we use in circuits.

Circuit Experiment

• You can build a very basic electrical circuit and find out what happens when a circuit is “open” compared with when it’s “closed”.

• Here’s what you need:

– Penlight bulb

– Flashlight battery

– Two 6" pieces of insulated wire (any kind will work)

– Tape to keep the wire on the end of the battery

– A small piece of thin flat metal to make a “switch”

– Small block of wood

Here’s What To Do!

1. Make a switch:• Take the block of wood and stick one thumb tack in• Push the other thumbtack through the thin piece of flat metal• Push the thumb tack into the wood so that the piece of metal can touch the

other thumb tack (see picture)2. Connect the first piece of wire to a thumbtack on the switch.3. Place the light bulb in the center of this wire piece.4. Tape the end of the first piece of wire to one end of the battery.5. Tape your second piece of wire to the opposite end of the battery.6. Attach the end of your second piece of wire to the remaining thumbtack on the switch.

You’ve created an electrical circuit

Circuits

• The number of electrons we are willing to let across the circuit at one time is called “current”.

• We measure current using amperes, or “Amps”.• For example:

– One AMP is defined as 625,000,000,000,000,000,000 (6.25 x 1018) electrons moving across your circuit every second.

• The amount of charge between the sides of the circuit is called “voltage”. We measure Voltage in Volts.

• The word Volt was named after a scientist, Alexander Volta, who built the world’s first battery.

• One volt is defined as the amount of electrical charge needed to make one Coulomb(625,000,000,000,000,000,000 electrons) do one specific amount of work – which is labelled one joule.

Parallel Circuits!

• When we have only one circuit that electrons can go through to get to the other side we call it a “series circuit”.

• If we were to set up another circuit next to the first one, we would have two circuits between the charges. We call these “parallel circuits” because they run parallel to each other.

• You can have as many parallel circuits as you want. Parallel circuits share the same voltage, but they allow more paths for the electricity to go over. This means that the total number of electrons that can get across (the current) can increase, without

breaking either circuit.

Electric Motors

• An electric motor uses circuits wound round and round. These wound circuits are suspended between magnets.

• A motor works through electromagnetism. It has a coiled up wire (the circuit) that sits between the north and south poles of a magnet.

• When current flows through the coiled circuit, another magnetic field is produced.

Stored Energy and Batteries

• Energy cannot be created or destroyed, but it can be saved in various forms. One way to store it is in the form of chemical energy in a battery.

• When connected in a circuit, a battery can produce electricity.

• If you look at a battery it has two ends – a positive terminal and a negative terminal.

• If you connect the two terminals with wire, a circuit is formed. Electrons will flow through the wire and a current of electricity will be produced.

How The Chemical Reaction Takes Place In A Battery?

• A very simple modern battery is a zinc-carbon battery, called the carbon battery for short.

• This battery contains acidic material within and a rod of zinc down the center.

• When zinc is inserted into an acid, the acid begins to eat away the zinc, releasing hydrogen gas and heat energy. The acid molecules break up into

its components: usually hydrogen and other atoms. • The energy in that circuit can now light a light bulb in a flashlight or turn a

small motor. Depending on the size of the battery, it can even start an automobile.

• Eventually, the zinc rod is completely dissolved by the acid in the battery, and the battery can no longer be used.

Different Types of Batteries

• Different types of batteries use different types of chemicals and chemical reactions. Some of the more common types of batteries are:

– Alkaline battery: used in Duracell” and Energizer” and other alkaline batteries. The electrodes are zinc and manganese-oxide. The electrolyte is an alkaline paste.

– Lead-acid battery: these are used in automobiles. The electrodes are made of lead and lead-oxide with a strong acid as the electolyte.

– Lithium battery: these batteries are used in cameras for the flash bulb. They are made with lithium, lithium-iodide. They can supply surges of electricity for the flash.

Different Types of Batteries

– Lithium-ion battery: these batteries are found in laptop computers, call phones and other high-use portable equipment.

– Nickel-cadmium or NiCad battery: the electrodes are nickel-hydroxide and cadmium. The electrolyte is potassium-hyroxide.

– Zinc-carbon battery or standard carbon battery: zinc and carbon are used in all regular or standard AA, C and D dry-cell batteries. The electrodes are made of zinc and carbon, with a paste of acidic materials between them serving as the electolyte.

Food Another Method of Storing Energy

• Batteries store energy in a chemical process, but there are other ways of storing energy. Consider the “food chain” on our planet.

• Plants, like grass in a meadow, convert the sun’s energy through photosynthesis into stored chemical energy. This energy is stored in the

plant cells is used by the plant to grow, repair itself and reproduce itself.

• Cows and other animals eat the energy stored in the grass or grain and convert that energy into stored energy in their bodies.

• When we eat meat or other animal products, we in turn, store that energy in our own bodies. We use the stored energy to walk, run, ride a

bike or even read a page on the internet.

Food Another Method of Storing Energy