Science 9 Unit D Electrical Principles and Technologies

^What is electricity?^ ^Electricity comes from the Greek word electron, which means amber.^ Amber was used by a philospher Thales, to cause an attraction to materials ^It is a general term for the variety of things that result from the presence and flow of electric charge.^

^Electricity involves charges trying to find a balance, just like everything else in the world.^

^Lightning^ ^A thunderstorm starts as heated moist air in the atmosphere rises, resulting in the formation of thunderclouds.^ These clouds grow higher and higher as the warm updraft continues, carrying the moisture higher in the atmosphere where it condenses to form ice crystals.

Since lightning heats the surrounding air to temperatures hotter than the surface of the Sun, there is an EXPLODING sound, which we call THUNDER.

^Tesla Coil^ Named after its inventor, Nikola Tesla ^Used to see and study electricity^ Can be seen today in video games and movies, where the coils appear as weapons typically firing bolts of electricity at enemies^

^Jacob’s Ladder^ a.k.a high voltage traveling arc ^a device for producing a continuous train of large sparks which rise upwards^

Learning Outcomes Distinguish between static and current electricity, and identify example evidence of each Define electrical discharge providing an example Identify electrical conductors and insulators Assess the potential danger of electrical devices, by referring to the voltage and current rating (amperage) of the device; and distinguish between safe and unsafe activities

Topic 1 Electrical energy can be transferred and stored.

*Static Electricity* ^A stationary (still; motionless) electric charge^ ^a.k.a electrostatics^ ^an electrical charge caused by an imbalance of electrons on the surface of a material^

Examples: Hair raising because of a balloon Lightning Sparks from clothes after they’ve been in the dryer

This is an example of static electricity gone bad. caused by a refueling fire ignited by static electricity

^Static is just an electrical charge that can be transferred from place to place.^

^Recall^ ^An atom is made up of tiny, particles^ ^Protons: positive charges^ ^Electrons: negative charges^ ^Static Electricity happens when the charges on the particles cause either an attractive or repulsive force between them.^

^If two neutral charges are put together, there is no movement (attraction or repulsion).^

*The Laws of Electrical Charges* 1.^Like charges repel (keep away from) one another.^ 2.^Opposite charges attract (pull towards) one another.^

Remember lightning?

*Charge separation* ^A charged object will also attract to a neutral or uncharged object.^ ^This is also known as Charged Polarization^

^How does this happen?^ ^This happens by causing a concentration of like charges in specific areas of a neutral object.^ Ex: A negatively charged ball brought close to your neutral finger, causes electrons to repel and protons to come forward.

*Electrical Discharge* ^The sudden transfer of electrical charge from one object to another, indicated by a spark.^

^Van de Graaff Generators^ ^An electrostatic machine which uses a moving belt to accumulate very high voltages on a hollow metal globe.^ 1929, Physicist Robert J. Van de Graaff Applications for this high voltage generator include driving X-ray tubes, food sterilization and processing, and for nuclear physics experiments

^ Schematic view^

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Testing your understanding You rub your feet across a floor and electrons transfer from you to the floor. Are you now negatively or positively charged?

A neutral object contains no charge. Is this statement true or false?

You bring a negatively charged rod close to some tiny pieces of plastic. Some of the pieces jump up to the rod, but as soon as they make contact, they immediately fly away from the rod. Explain what happened.

Unit D Topic 2

^Electric Eel^ Species of fish (not an eel; knifefish) capable of generating powerful electric shocks, which it uses for both hunting and self-defenseelectric has three pairs of organs that produce electricity

*Electrical Current* ^the steady flow (movement) of charged particles^ Used to operate electrical devices ^Unlike the charges in static electricity, which charge and discharge.^

Works under two conditions: 1.^Has to have an energy source^ 2.^There must be a *circuit* (complete path that charged particles need to flow through)^

The SI (International System) Unit of electric currents is the *ampere (A)*.  ^rate at which an electric current flows^  ^amount of charge per second^  Specifically, 1 Coulomb of charge per second.  An ampere can also be called an “amp”. ^Named after André-Marie Ampère, one of the main discoverers of electromagnetism.^

Current in amps of Common Electrical Devices  60-W light bulb = 15 A  Microwave Oven = 5 – 8 A  Electric Kettle = 13 A  Television = 4 – 5 A  TV Antenna Booster = < 1 A  Ceiling Fan = 4 A

A continuous flow of electrical charge is easily produced. It is the transfer of the charge that is the tricky part.

*Conductors* ^A material that electric charge can move through easily^

^Conduction of electricity through wires allows for the transfer of electrical charge from place to place.^

Think about an electric power grid

Electricity is usually transmitted over long distance through overhead power transmission lines. Underground power transmission is used only in densely populated areas (such as large cities) because of the high cost of installation and maintenance and because the power losses increase dramatically compared with overhead transmission unless superconductors and cryogenic technology are used.

^Circuits ^Since they are complete paths that charged particles need to flow through, Circuits control the flow of electricity.^ ^Usually they flow along solid metal wires, but can flow through gases or other fluids.^

^A circuit may include: ^A conductor^ ^An energy source^ *Load* ^device in a circuit that converts electrical energy to another form of energy^

*Electrical Energy* ^Energy of charged particles ^It is transferred when electrons travel from place to place

*Voltage* ^A measure of how much electrical energy a charged particle carries.^ ^Measured in volts (V)^ Named after Alessandro Giuseppe Antonio Anastasio Volta; an italian physicist known especially for the development of the electric battery in 1800

You will make a battery in high school… ^Volta demonstrated that when metals and chemicals come into contact with each other they produced an electrical current.^metals chemicalselectrical In his research, Volta placed together several pairs of alternating copper (or silver) and zinc discs separated by cloth or cardboard and soaked the cloth or cardboard in brine (salt water) to increase conductivity, and an electrical current was produced.coppersilverzincbrinecurrent

*Potential Difference* ^Another name for Voltage^ ^It is the change in the potential energy of electric charge compared to its potential energy at a reference point^ ^Energy delivered = Voltage x total charge ^ of electrons

*Voltmeter* ^Instrument for measuring potential difference in volts^ If there is more than one red terminal (positive), start measuring using the highest one and work your way down.

1 millivolt = 1/1000 of a volt 1 mV = V Recall Conversion Chart: km hm dam m dm cm mm kV hV daV V dV cV mV

How does current electricity differ from static electricity?

Suppose I have a voltmeter reading 15 mV, convert that to volts.

You require a high-current battery to start a large tractor. While shopping for this battery, should you be more concerned with the battery’s rating of volts or amps?