Electricity-Eletrical energy, static charge, electric force

What is electrical energy?

The energy of charged particles

What uses electrical energy?

• The human body-moving your eyes to read relies on electrical signals in your muscle, electrical signals help maintain breathing and heart beat

• Technology-Eg. touch sensitive screens and robots

How does electrical energy come to be?

• Energy is neither created or destroyed

• It is transformed from one kind of energy to another kind of energy (many types of energy can be transformed into electrical energy)

What are the types of energy?

• Mechanical energy

• Kinetic energy

• Potential energy

• Chemical energy

• Solar energy

• Nuclear energy (nuclear fusion and nuclear fission)

• Thermal energy

What is mechanical energy?

• The sum of kinetic and potential energy

What is kinetic energy?

• The energy of motion

What is potential energy?

• Stored energy that a system has due to its position or condition eg. water at the top of the waterfall

What is chemical energy?

• Energy stored in chemical bonds and released when a chemical reaction occurs

• Eg. batteries store chemical energy

• Eg. chemical energy stored in animals and plants is called biomass

• Eg. Fossil fuels store chemical energy

What is solar energy?

• Energy carried by electromagnetic radiation given off by the sun

• Fossil fuels and biomass result from energy from the Sun being captured by plants and plant like organisms

What is nuclear energy?

• Energy generated by forming new atoms

• Nuclear fusion and nuclear fission

What is nuclear fusion?

• New atoms are made as smaller atoms collide and fuse (occur in sun and stars)

What is nuclear fission?

• New atoms are made by splitting larger atoms (done with nuclear reactors on earth)

• Most of the energy is thermal energy, which is used to boil water into steam

• Pressure from the moving steam turns turbines connected to generators

What is thermal energy?

• Energy due to the rapid motion of particles that make up an object, detected as heat

• Sources include nuclear reactions or from Earth’s interior (geothermal energy) where steam and hot water form naturally

• Eg. Geysers, volcanoes, hot springs,

What is a generator system?

• A system that transforms kinetic energy to electrical energy

What is a turbine?

• Steam, water or wind cause the turbine to spin

What is a shaft?

• As the turbine spins, the shaft spins

What is a generator?

• Kinetic energy of the spinning shaft is transformed into electrical energy inside the generator

How does Canada and B.C. generate electrical energy?

• Mostly comes from river flow, fossil fuels and nuclear reactions

• B.C. uses river flow and fossil fuels

• River flow is the main source (hydroelectricity)-water flowing freely in a river turns a turbine

• Thermal energy from burning coal is used to boil water into steam

• No nuclear reactors in B.C.

What are other energy sources?

• Wind

• Sunlight

• Geothermal sources

• Waves and Tides

How can wind be used to generate electricity?

• Kinetic energy of wind is transformed into electrical energy as the moving air turns the turbine of a generator system

How can Sunlight be used to generate electricity?

• Photovoltaic cells transform the energy of visible light to electrical energy

• When visible light strikes electrons in the photovoltaic cells, the electrons absorb enough energy to flow freely and generate electrical energy

How can Geothermal sources be used to generate electricity?

• Where Earth’s crust is thin and molten rock comes close to the surface, hot steam can be used to turn turbines to generate electrical energy

How can waves and tides generate electrical energy?

• Tides and the rise and fall of waves can turn turbines to generate electrical energy

• What is static charge? (static electricity)

• Electric charge that stays in one place until it is discharged to other objects or to the air

• Measured in coulombs: the unit of electric charge

• It takes the addition or removal of 6.25×10^18 electrons to produce 1C of charge

Explain the positive and negative charge in the atom.

• Atoms contain protons and neutrons in their nucleus and electrons outside the nucleus

• If the number of positive charges equal the number of negative charges, the object is neutral

Explain what happens and how on Uncharged materials.

• Before two materials are rubbed together, they have equal numbers of positively charged protons and negatively charged electrons

• If the number of positive charges equals the number of negative charges, the object is neutral

• In a solid material the positive nucleus stay in the center of the atom, but the electrons can be rubbed off a material (all solid materials are charged by the transfer of electrons)

Explain what happens to and how on Charged materials.

• If electrons rubbed off one material, the protons stay behind and the material become electrically charged

• the material that gains the electrons also become electrically charged

• Electrically charged materials have an unequal number of positive and negative charges

• When a neutral atom looses electrons it becomes positive

• When a neutral atom gains electrons it becomes negative

What is friction?

• Occurs when objects rub against each other

• Result in one object loosing electrons and the other object gaining electrons

• Electrons will either stay on the surface of the new material or travel through it

What are insulators?

• Materials that do not allow electrons to move easily

• Can retain a static charge

• Eg. Glass, plastics, ceramics, dry wood

What are conductors?

• Materials that allow electrons to move easily

• Will allow a charge to flow

• Eg. Metals

Explain conductivity.

• An indication of how easily charges travel through a material

• Electrons can move through almost all metals (conductors), can move through some metals more easily than others

• The higher the conductivity of a material, the more easily electrons can move through

What represents static charge in a much larger scale?

• Lightning

• Rubbing caused by air moving around

• Thunderclouds bottom is usually negative and top is usually positive

What is a Van de Graaff Generator and how does it work?

• Uses friction to produce a large static charge on metal dome

• A moving belt produces a static charge at the base of the gnerator

• The belt carries the charge to the metal dome where it is collected

What is grounding?

• Connecting a conductor so that electric charge flows into Earth’s surface

What is a force?

• A push or a pull

What is a contact force?

• Forces that can have an effect only on objects when they touch

What is action at a distance force?

• Forces that can have an effect on an object without touching it

• Electric force: push or pull between charged objects

• Example of an action at a distance force

What are the laws of static charge?

• Like charges repel: positive and positive charges repel, and negative and negative charges repel

• Opposite charges attract: Positive and negative attract

• Neutral objects are attracted to charged objects: Positive and neutral attract, and negative and neutral attract

What does coulomb’s law state?

• If the amount of charge increases, the electric force increases

• If the distance between charged objects increases, the electric force decreases

What is charging by conduction?

• Objects become charged through contact

• When objects touch, electrons move from one object to the other

• Ex. walking across a carpet and touching a metal doorknob

What is charging by induction?

• When objects are charged without touching or making any direct contact

• Electrons do not move from one object to the other

• Electrons reposition themselves in the object that becomes charged

• Because no electrons are transferred, the charge is only temporary

• ex. dust on tv screen

How is the attraction of neutral objects explained?

• Induction explains why neutral objects are attracted to charged objects

• Neutral objects are attracted to charged objects because the neutral objects are temporarily charged by induction

What is an example that proves the attraction of neutral objects?

• A balloon that is rubbed on a sweater (charged by conduction) and become negatively charged will stick to a neutral wall

• The balloon’s negative charges repel the wall’s negative charges

• The wall becomes positively charged by induction

What are electrochemical cells?

• Convert chemical energy into electrical energy

What is a battery?

• A single electrochemical cell or combination of electrochemical cells connected together

What is a terminal?

• End points of an electrochemical cell/battery where connections are made

• Negative terminal: end where electrons accumulate

• Positive terminal: end that has lost electrons

What are electrodes and electrolytes?

• The two terminals in an electrochemical cell/battery are called electrodes

• The electrodes are in an electrolyte, which is a substance that conducts electricity

What are the two groups of cells?

• Dry cells: electrolyte is a moist paste (used in flashlights and watches)

• Wet cells: electrolyte is a liquid (used in cars and motorcycles)

How is the amount of voltage determined?

• The amount of voltage that is produced in an electrochemical cell depends on the types of metal (electrodes) and electrolytes used

• Most electrochemical cells produce 1.5V or 2V

What is electric potential energy?

• Energy is the ability to do work

• Electric energy can do work

• When unlike charges are moved farther apart, they gain electric potential energy

• Electric energy that is stored is potential energy

• Electric potential energy: the electrical energy stored in an electrochemical cell

• Electric energy that is moving is kinetic energy

What is voltage?

• The amount of electric potential energy per coulomb of charge

What is Volt (V)?

• The unit of measure for voltage

What is a voltmeter?

• Measures voltage between two locations of charge separation

How do you measure the actual electric potential energy?

• Product of both the voltage and the amount of charge

• Energy=volt*charge

What is an electric current?

• A complete pathway that allows electrons to flow

How does energy move around a circuit?

1. Chemical energy in the battery separates positive and negative charges and gives electrons on the negative terminal electric potential energy

2. Electrons move across the wire as they are repelled by the negative terminal and attracted to the positive terminal

3. Potential energy is transformed into other forms of energy when it passes through a load Eg. in buzzers it is transformed into sound energy

What are the main components of a circuit?

• Source

• Conductor

• Load

• Switch

What is a source?

• Where the electrical energy comes from (electrochemical cell or battery)

What is a conductor?

• The wire through which electric current flows

What is a load?

• A device that converts electrical energy into other forms of energy

• Ex. light bulbs, heaters, radios

• As electrons pass through a load, they lose energy as electrical energy is converted into another type of energy

• A load resist the flow of current

• Electrons in the current collide with atoms that make up the load or with each other

• Collisions interfere with the flow of current

What is a switch?

• A device that can turn the circuit on or off by closing or opening the circuit

• Controls the flow of current

What is a circuit diagram?

• A diagram that uses symbols to represent different components of an electric circuit

Why are electrons so pushy?

• All electrons have a negative charge

• This means electrons repel/push each other

• Electrons in every part of a circuit are pushing each other, so when a circuit is closed the load works immediately

Explain current electricity.

• When a battery is connected to a complete circuit it causes electrons to move

• Moving electrical charges form an electrical current

• Chemical energy from a source causes charges to move through a conductor, carrying energy to an electrical device

• The moving charges are called an electrical current

What is current electricity?

• The continuous flow of charge in a complete circuit

What is an electric current?

• The amount of charge passing a point in a conductor every second

• Symbol for current: I

• Measured in Amperes (A)

• One coulomb of charge passing a given point per second

What is an ammeter?

• Device used to measure the current in a circuit