Download
1 / 60
600 likes | 689 Vues
Section questions. Hip – Hip – Huzzah!! . Section 10.1. What happened on August 14 th , 2003 at 4:11? 50 million people in Ontario and the northeastern US were plunged into the largest electrical blackout in North American history. What were you doing then and how were you affected?
E N D
Section questions Hip – Hip – Huzzah!!
Section 10.1 • What happened on August 14th, 2003 at 4:11? • 50 million people in Ontario and the northeastern US were plunged into the largest electrical blackout in North American history. • What were you doing then and how were you affected? • Various answers • What is an “energy grid”? • It is a huge, interconnected system of electricity networks (which includes electrical generating stations, transmission lines, and distribution stations). • Why does an energy grid have to balance supply with the demand for electricity? • It must maintain a balance of supply and demand because electricity cannot be stored for long after it is generated. If it isn’t and a generator is overloaded, that part of the energy grid is disconnected and electricity will be sent along alternative paths.
Section 10.1 A SHOCKING EXPERIENCE • What is an electric shock? • It is caused by electric charges that gather or accumulate, then are released very quickly. • How are lightning and an electric spark similar? • They are the same thing, just different in size – they are caused by electric charges, which are charged particles that exert an electric force on each other.
Section 10.1 ELECTRICALLY CHARGED PARTICLES • What is the charge of a proton? • Positive • What is the charge of an electron? • Negative • What is the charge of a neutron? • No charge or neutral • Can an atom lose protons? • No, they are bound to the neutrons in the nucleus. • Can an atom lose electrons? • Yes, they orbit around the outside of the nucleus and can move from one object to another.
Section 10.1 FRICTION AND THE MOVEMENT OF ELECTRONS • What has happened when an object creates a static charge? • Electrons have moved from one object to another through some method, and that electric charge builds up on the surface of the object. • What is the difference between an object that has a negative charge and the same object when it has a positive charge? • A negatively-charged object has more electrons than protons, whereas a positively-charged object has more protons than electrons. • How does rubbing two objects together sometimes result in the building of a static electric charge? • The force of friction can remove electrons from one object and cause them to transfer to the other object. • Where does the word, “electricity” come from? • It comes from the Greek word electron, meaning amber, which is fossilized tree resin. It has been used for thousands of years to study static electricity.
Section 10.1 ELECTRON AFFINITY • What does “electron affinity” mean? • It is the tendency of a substance to hold on to the electrons. • If you rub nylon and steel together which one becomes negative and why? • Steel becomes negative because steel is lower on the triboelectric series. • If you rub amber and silk together which one becomes negative and why? • Amber becomes negative because amber is lower on the triboelectric series. • If you rub Teflon and human hair together which one becomes negative and why? • Teflon becomes negative because Teflon is lower on the triboelectric series. • If you rub ebonite and cat fur together which one becomes negative and why? • Ebonite becomes negative because ebonite is lower on the triboelectric series.
Section 10.1 LAWS OF ATTRACTION AND REPULSION • What do unlike (or opposite or dissimiliar) charges do? • They attract. • What do like charges do? • They repel. • What happens between a neutral object and a positive object? • The neutral object is attracted to the positive object. • What happens between a neutral object and a negative object? • The neutral object is attracted to the negative object.
Section 10.1 • Copy the following in your notebook and write if they would attract or repel each other in the blank in the middle. positive attracts negative positive repels positive positive attracts neutral Negative repels negative negative attracts positive negative attracts neutral • Memorize and understand the laws of attraction and repulsion. • Opposite charges attract; Like charges repel; Charged objects attract neutral objects. • What is Charles-Augustine de Coulomb famous for? • He made several important discoveries; he showed that when two charged objects are placed closer together, the attraction or repulsion increases. When the charged objects are moved farther apart, the attraction or repulsion decreases. The metric unit for electric charge is named the coulomb (C). • How many electrons are in 1 coulomb? You will need to remember this number. • There are 6.24 x 1018 electrons in one coulomb.
Section 10.1 ELECTRICAL INSULATORS AND CONDUCTORS • What is conductivity? • It is the ability of materials to allow electrons to move freely in them. • What does an insulator do? • It is a solid, liquid, or gas that resists or blocks the movement of electrons. • If you wanted electricity to move from one location to another location, would you use a conductor or an insulator? • I would use a conductor, because those materials allow electrons to change positions. • If you had electricity traveling through a wire and wanted to protect yourself from electric shock what would you cover the wire in, aluminum or rubber? • I would cover the wire in rubber because it would not allow the electrons (the electric shock) move freely.
Section 10.1 key concept review • 2, • Friction is the force resisting the relative motion of two surfaces in contact. • When two neutral objects, like glass and cotton, are rubbed together, electrons are transferred by the rubbing from the glass to the cotton. This happens because glass tends to lose electrons more so than cotton, because glass is higher on the triboelectric series. Glass ends up with a positive charge, while cotton ends up with a negative charge. • 3, • A neutral object is NOT charged, but contains and EQUAL AMOUNT of positive and negative charges (protons and electrons). • 4 (but change the word “opposite” to “unlike”), • Opposite charges attract; like charges repel. • 6, • It could have an equal amount of protons to balance the charge. • 7, • A conductor allows electrons to move freely, whereas an insulator resists their movement. • Any metal. • Wood, plastic, rubber.
Section 10.1 key concept review • 8, • A fair conductor only allows SOME movement of electrons. • The human body, soil, impure water. • 9 • Electric charges will spread through the water and cause you injury. • 10, • They do not because neither one is higher or lower on the triboelectric series, so neither one has a larger tendency to gain or lose electrons.
Section 10.1key concept review • 11, • 13 • You are sitting in a conductor, which makes it easily for lightning to flow through. The water’s not pure either, so it’ll make it easier for the charges in the lightning to flow through that. Both are potentially dangerous/fatal. • Yes it would partially because you wouldn’t have to worry about the lake killing you, as it is now an insulator.
Section 10.2CHARGED OBJECTS • What is an electroscope used for? • It can detect static charge. • What are the thin metal flaps in an electroscope called? • They are called leaves. • Which law of charges explains why the leaves of an electroscope separate when a charged object is brought near it? • Like charges repel. • What is electrostatics? • It is the study of static electric charges.
Section 10.2DETECTING STATIC CHARGE • Draw the following three electroscopes, making sure that the number of electrons illustrates what is happening. • A closed neutral electroscope. • An electroscope that is separated with a negative charge. • An electroscope that is separated with a positive charge. CHARGING BY CONTACT • When you charge a neutral object by contact, what charge does the neutral object get? • The same charge as the charged object.
Section 10.2induction • What is induction? • It is the movement of electrons within a substance caused by a nearby charged object, without direct contact between the substance and the object. • Why does rubbing a balloon on your hair make both the balloon and the hair charged? • Electrons transfer from your hair to the balloon, meaning your hair has more protons than electrons and is now positive, while the balloon has more electrons than protons and is now negative charging by friction. • What type of material do you need to build up a static electric charge, a conductor or an insulator? • An insulator. • If you bring a negatively-charged balloon near a wall but don’t touch it, what charge does part of the wall get? • It gets a positive charge. • If you bring a negatively-charged balloon near a wall where do the electrons in the wall go? • Further back into the wall because they are repelled by the negative charges in the balloon.
Section 10.2charging by induction • What does “grounding” mean? • It is the process of connecting a charged object to Earth’s surface. • When you induce an electroscope with a negatively-charged object, what charge does the electroscope get? • It gets a positive charge. • What do you need to do to make an induced-charge permanent? • You need to ground the electroscope while holding the charged object near it to provide a path for electrons to escape from the negatively-charged object, or a path for electrons to get from the ground closer to the positively-charged object.
Section 10.2 ELECTRICAL DISCHARGE • When you get an electrical spark, does the electricity discharge by contact, friction or induction? • Induction. LIGHTNING • What charge does a storm cloud normally have, positive or negative? • It has a negative charge. • What charge does a storm cloud normally induce in the ground? • It induces a positive charge.
Section 10.2electrostatic generators • If a Van de Graaff generator has a lower pully made of nylon and a belt made of rubber, which part get negatively-charged, the pully or the belt (look at the Triboelectric series). • Belt gets negatively charged. • If a Van de Graaff generator has a upper pully made of Teflon and a belt made of rubber, which part get negatively-charged, the pully or the belt (look at the Triboelectric series). • Teflon gets negatively charged.
Section 10.2key concept review • 1, • They are the same, electrical discharges. • 2, • A negatively-charged object touches a neutral object. • A positively-charged object touches a neutral object. • 3, • It becomes temporarily charged because when the charged object is brought near, the like charges are repelled by this charged object, into the leaves, inducing an opposite temporary charge (from the charged object) on the electroscope. • 4 • While holding a charged object near the electroscope, use your finger to ground the electroscope. Take your finger away while still holding the charged object near. Then take the charged object away, and your electroscope is now permanently charged through induction.
Section 10.2connect your understanding • 6, • Electrons are being transferred in an electrical discharge from you to the metal to the ground or vice versa. It will make you neutrally charged. The shopping cart is providing a path to or from the ground for the electrons to use. • Again, the air is providing a path for electrons to travel to the ground, neutralizing the cloud more. • 7, • Charges would have no path to travel down the metal rod into the leaves. • 8, • This happens because like charges repel. • This happens because opposite charges attract. • 9 • The metal rod would receive the shock.
Section 10.3LIGHTNING STORM AWARENESS • Why are large buildings fairly safe during a lightning storm? • They are safe because they will be properly grounded if there is a strike. • What should you do during a lightning storm in order to be safe in a car? • Roll up the windows and don’t touch metal parts of the car. • Why is it that men during the summer are more often stuck by lightning than women during the fall? • Men are generally taller, making a shorter path for the lighting to travel and more likely to be struck.
Section 10.3 LIGHTNING RODS • What part of the tree conducts the static discharge when a lightning bolt strikes a tree? • The sap inside the tree conducts the electricity down to the ground. GROUNDING STATIC CHARGES ON VEHICLES • The textbook doesn’t say it, but when a moving car builds up a static charge what are the two different types of materials that are rubbing together? • Air and particles in it, and metal from the car. OR Rubber from the tires and asphalt/cement/dirt/gravel from the ground • What device can you put on a car that “grounds” the car and prevents a static charge from forming? • A grounding strap grounds the car. • The textbook doesn’t say it, but when a moving plane builds up a static charge what are the two different types of materials that are rubbing together? • Air and particles in it, and the metal on the plane are rubbing together. • What device can you put on a plane that “grounds” and prevents a static charge from forming? • Dissipaters are needle-like rods that disperse static charges into the air. • What type of material (insulator or conductor) do you use to prevent static electric charges from forming? • Conductors are used.
Section 10.3 STATIC CHARGES AND FLAMMABLE MATERIALS • Why is a car with a static electric buildup dangerous around gas stations? • Gas is flammable and one static spark can ignite it. REDUCING STATIC CHARGES IN THE HOME • What would build up a larger amount of static cling, a load of dirty silk clothes or a load of dirty silk and wool clothes? • A load of dirty silk and wool clothes because they are made of different material, so when they are rubbed together they will be charged by friction. • When do clothes in a drier build up a static charge – when the laundry is wet or dry? • More charges build up in dry air like during winter, because dry air acts as an insulator. • How do drier sheets reduce static cling? • It adds a thin layer of waxy chemicals to the surface of clothes so there is less friction between the surfaces and therefore fewer unlike charges to attract each other. • What are the four different methods for reducing charge build-up in a computer room with a carpet? • Use an antistatic mat for your feet; increase the moisture in the air with a humidifier; spray the carpet with antistatic spray; wear an antistatic wrist strap.
Section 10.3making use of static charges • Why do industrial spray painters charge their spray paint with a negative charge? • There is less waste due to bounce and overspray and the finish is smooth and uniform. • Why don’t industrial spray painters get spray paint on the floor and walls behind the object they are painting? • The paint is attracted to the surface it is painting, because it is the opposite charge of the paint. That attraction is so strong that it will be more attracted to the object instead of neutral things around it. • In step 1, what is the charge on the selenium drum? • It is positively charged. • When the selenium drum is in the dark does it behave as a conductor or an insulator? • Insulator. • When the selenium drum is in the light does it behave as a conductor or an insulator? • A type of conductor called a photoconductor. • What happens to the charge on the selenium drum when light is projected on it? • The area on the drum becomes conductive and loses its charge, becoming neutral. • What doesn’t happen to the areas of the selenium drum that is still dark when light is projected on it? • They do not become neutral and remain positively charged. • What charge is on the toner (ink)? • It is charged negatively.
Section 10.3environmental applications • What does an electrostatic precipitator do? • Through the use of static electric charges, it cleans gas by removing tiny pollutant particles and sends clean gas out into the air. The particles in the gas are charged when it is sent through pipes, charging the particulate matter negatively. The gas moves through an area with positively charged plates, which attract the negative pollutant matter and remove them from the gas.
Section 10.3key concept review • 1 (you could get struck by lightning is not enough of an answer – why is a tree more dangerous than a shrub?), • Trees may be the highest point in the area, which makes it more likely that it will be struck by lightning. • 3, • Vehicles build up static charge through friction between the vehicles outer surface and the air. • 4, • It grounds the truck, allowing excess static charge to be transferred to the ground so that the flammable liquid inside the truck does not get ignited by an electric spark. • 5, • The paper may still be charged when it comes out of the photocopier. • 6 • Antistatic dryer sheets, antistatic spray, electrostatic precipitators, and photocopiers are four applications that use electrostatic principles.
Section 10.3connect your understanding • 7, • It is so large with so many positive and negative charges, that overall it is not affected by any electron transfers and is considered neutral. • 8, • When they are brought through pipes, the particulate matter becomes negatively charged and so is attracted to the positively charged plate. • 9 (how does the insulation protect the electronics?), • This is so your body does not transfer its charge into the metal tool, and then into the electronic equipment, damaging it. • 10, • Through the third law, charged objects attract neutral objects. • 11, • Water can be pure and therefore an insulator and not conduct electricity; water is also only a fair conductor, and so it is not great at conducting electricity at the best of times. • 12 • You could get rid of your carpet, use antistatic spray and antistatic dryer sheets to reduce or eliminate these problems.
Section 11.1current electricity • Why isn’t static electricity useful for operating electrical devices? • They build up and discharge, but they do not flow continuously. • How do you want electrons to flow when you operate an electrical device? • You need a steady flow of electrons. • What are the two things that this section says you need for a circuit? • The flow of electrons requires an energy source and the path the electrons follow must be complete. • What is current electricity? • It is the continuous flow of electrons in a circuit.
Section 11.1electric circuits • What is an electrical load? • It is a device that converts electrical energy to another form of energy. • What does an electrical load do to electrical energy? • It converts it to another form of energy. • List the four things you need to make an electrical circuit. I have scrambled the letters of each one to help you remember them. (reengyreoucs, ploceemtthap, chwist, alod) • Energy source, complete path (connector/conductor/wires), switch, load • What is an open switch? • It means that there is a break in the path, so the electrons cannot flow through the circuit. • What is a closed switch? • This means the circuit is complete and electrons can flow.
Section 11.1electrochemical cells • What is an electrochemical cell? • It is a package of chemicals that converts chemical energy into electrical energy that is store in charged particles. • What is a battery? • It is a combination of electrochemical cells. • What is the difference between an electrochemical cell and a battery? • Battery contains many electrochemical cells. • Note: Usually an “electrochemical cell” is simply called a “cell”. • A cell is made of two different electrodes. What happens at each of the electrodes? • Electrons collect on one of the electrodes, making it negatively charged. The other electrode has lost electrons, so it is positively charged. • What does the electrolyte do in a cell? • It reacts with the electrodes and conducts electricity.
Section 11.1wet cells and dry cells • What is the difference between a wet cell and a dry cell? • Wet cells use a liquid electrolyte, while dry cells use a paste electrolyte. • Where do you commonly find wet cells? • You find them in cars and other vehicles. • Where do you commonly find dry cells? • You find them in flashlights, hand-held video games devices, cameras, and watches.
Section 11.1 RECYCLING AND RECHARGING DRY CELLS • What do dry cells (common batteries) commonly have in them that makes them bad for the environment to simply throw away? • They contain toxic materials like heavy metals, including nickel, cadmium, and lead. FUEL CELLS • What makes a fuel cell more reusable than reusable batteries? • The cell is not used up like ordinary cells would be because as the electricity is produced, more fuel is added.
Section 11.1potential difference • What has more potential energy, an apple on a tree or an apple that has fallen from a tree? • The apple on the tree has more potential energy. • What is another term for potential difference? • Another term for potential difference is voltage. • Explain what is meant by the term potential difference? (this is very important to understand) • The difference in electric potential energy between two points in a circuit is termed potential difference or voltage. This difference causes current to flow in a closed circuit. The greater the potential difference in a circuit, the greater the potential energy of each electron. • What is potential difference measured in (what units is it measured in)? • It’s measure in volts (V). • What is the name of the equipment that you measure potential difference with? • It is called a voltmeter.
Section 11.1current • When you turn on a circuit, do all the electrons along the wire move towards the negative terminal or do the electrons all have to start from the negative terminal? • The electrons start from the negative terminal. • What is electric current? • It is a measure of the amount of electric charge that passes by a point in an electrical circuit each second. • What is the difference between direct current and alternating current? • Direct current only flows in one direction, while alternating current flows back and forth at regular intervals. • What is a common source of DC? • A common source of DC is batteries. • What is a common source of AC? • A common source of AC is wall outlets or sockets.
Section 11.1 MEASURING CURRENT • What is the name of the equipment that you measure current with? • You measure current with an ammeter. • What is the unit current is measured in? • Current (I) is measured in amperes or amps (A). CURRENT ELECTRICITY AND STATIC ELECTRICITY • What is the difference between current and static electricity in relation to current? • Current electricity is the flow of electrons in a circuit through a conductor; static electricity is the electric charge that builds up on the surface of an object. Static electricity discharges when given a path, but does not continue to flow.
Section 11.1ELECTRON FLOW AND CONVENTIONAL CURRENT • What colour is the positive terminal of an ammeter? • It is red. • What colour is the negative terminal of an ammeter? • It is black. • What terminal do you connect the red terminal of an ammeter to when measuring current in a circuit? • You connect it to the positive terminal.
Section 11.1resistance • What is resistance? • It is the degree to which a substance opposes the flow of electric current through it. • What type of substance has more resistance, a conductor or an insulator? • An insulator has more resistance. • What unit is resistance measured in? • It is measured in ohms (Ω). • What does resistance do to the energy in electricity, use it up or push it backwards? • It uses it up, converting the electrical energy into other forms of energy.
Section 11.1resistance • What is a resistor? • It is a material that can slow current flow. • Why does the filament in a light bulb produce light? • It has a high resistance to the electron’s electrical energy and that causes it to heat up and produce light. • When does a circuit have a higher potential difference, before it enters a resistor or after it enters a resistor? • It has a higher potential difference before it enters a resistor. • What happens to a circuit’s potential energy when the electrons leave a resistor? • The potential energy has been converted to another form of energy, and so it decreases.
Section 11.1resistance • List some of the materials that resistors are made out of. • Some materials that resistors are made out of are heat-resistant metal with insulating cores, as well as those materials mixed with carbon. • What would have less resistance, a thick wire or a thin wire? • A thin wire would have more resistance because there is not as much space for the electrons to get through.
Section 11.1key concept review • They are composed of an electrolyte and two electrodes; an electrolyte can be a liquid or a paste that conducts the electricity produced by the ionization of the electrodes, usually zinc and copper.A reaction is produced between the electrolyte and electrodes in a wet cell, which creates electricity. • They flow from the negative end of the source to the positive end. • Voltmeters measure potential difference.Potential difference it measured in volts (V). • Ammeters measure current.Current is measured is amperes or amps (A). • Potential difference is the pushing force of electrons, while current is the number of moving electrons.
Section 11.1key concept review • DC flows only in one direction, while AC flows back and forth in intervals. • An electric load converts electrical energy into another type of energy (i.e. heat, light, sound, etc).Some examples of electrical loads are lights, motors, and resistors. • It is the degree to which a substance opposes the flow of electrons through it. • It slows down the movement of electrons and converts the electrical energy into other forms of energy. • The four factors affecting resistance in a wire are the following: the material, the cross-sectional area or thickness, the length, and the temperature.
Section 11.2 • What are the two rules you need to follow when drawing a circuit diagram? • Always use a ruler to draw straight lines for the conducting wires. • Make right-angle corners so that your finished diagram is a rectangle. • What is wrong with the circuit diagrams shown here? • The first rule isn’t obeyed. • The second rule isn’t obeyed. • No electrical symbols are used. • For practice, draw and label each of the symbols for the following components found in a circuit diagram. • wire • battery • light bulb • resister • switch • voltmeter • ammeter
Section 11.2series circuits • What is a series circuit? Write down the second sentence, the one that starts, “A series circuit has only one …” • …path along which electrons can flow. • Recall that current is the amount of electrons flowing through a circuit each second. In a series circuit is the current at the end of the circuit less, the same or more than the current at the beginning of the circuit? • The TOTAL current is the same. • Does adding more resistance in a series circuit increase or decrease the current? • Adding more resistance will decrease the TOTAL current. • If you add more lights in a series circuit does that make the light brighter or dimmer or do they stay the same? • Adding more lights will make all the lights dimmer in a series circuit.
Section 11.2parallel circuits • What is the full explanation of a parallel circuit? • It is an electric circuit in which the parts are arranged so that electrons can flow along more than one path. • If one path in a parallel circuit is cut, will the rest of the circuit still be able to work? • Yes, it will still be able to work. • Does the addition of a new path in a parallel circuit increase, keep the same or decrease the total resistance? • It decreases the total resistance of the circuit. • What does most of the current in a parallel circuit go through, the path with the most resistance, all paths equally or the path with the least resistance? • Most of the current will pass through the path with the least resistance. • What is the same along each path in a parallel circuit, the voltage, the current or the resistance? • The voltage is the same along each path in a parallel circuit.
Section 11.2 • Complete the following table:
I4=5A I1=5A IT= 5 A I23=5A I5=5A I1= 2A I2=3A IT= 5A Section 11.2 • What is the current at each of the points of the following circuits?
V1= 5V V2=5V VT= 5V Section 11.2 • What is the voltage at each of the points of the following circuits? V4=4V V1= 1V VT= 10V V23= 3V V5= 2V
Section 11.2 Draw circuit diagrams for circuits with the following. • A series circuit that has: • 1x cell • 3x lights • 1x open switch • A series circuit that has: • 1x 2-cell battery • 1x motor • 1x resister • 1x closed switch • A series circuit that has: • 2x 3-cell batteries • 3x lights • 1x open switch • A parallel circuit that has: • 2x 3-cell batteries in series • 2x lights (each in parallel) • 2x open switches (each switch controls one light) • A parallel circuit that has: • 2x 3-cell batteries in parallel • 2x resisters in parallel • 1x open switch (that controls both lights at the same time)
Section 11.3 • Why is the letter “I” used for current? (see box “words matter”) • The symbol “I” is used for current because it stands for INTENSITY. • What is the full name of the high school teacher who first worked out Ohm’s Law? • The high school teacher’s name is Georg Simon Ohm. • Ohm’s law is true so long as what stays the same? • As long as the temperature stays the same, Ohm’s law will hold true. • Complete the three equations: • V = IR • I = V/R • R = V/I
Section 11.3 • A current of 4.0 A flows through a 40 resister in a circuit. What is the voltage? • Given – I = 4.0A, R = 40 • Required – V = ? • Analysis – V = IR • Substitution and Solution • V = IRV = (4.0A)(40)V = 160V • Paraphrase – The voltage in this circuit is 160V. • A 30 V battery generates a current through a 15 resister. How much current does the battery generate? • Given – V = 30V; R = 15 • Required – I = ? • Analysis – I = V/R • Substitution and Solution • I = V/R • I = (30V)/(15)I = 2A • Paraphrase – The battery generates 2A of current.
