Exam Elementary Physics Chapter 22

Chapter 22 which force binds atoms together to form molecules? electrical in an electrically neutral atom the number of protons in the nucleus is equal to the number of? electrons that surrounded the nucleus a positive ion has more? protons than electrons strip electrons from an atom and the atom becomes? positive ion to say that electric charge is conserved is to say that electric charge? can be neither created nor destroyed the unit of electric charge,the coulomb, is the charge on? a specific number of neutrons the electric force between charges is strongest when the charges are? close together the electrical force between charges depends only on the charges? magnitude and Separation distance superconductors are noted for their? absence of electric resistance an electron and a proton? attract each other two protons attract each other gravitationally and repel each other electrically. By far the greater force is? the electrical repulsion to say that an object is electrically polarized is to say? it's charges have been rearranged a balloon will stick to a wooden wall if the balloon is charged? either positively or negatively electric potential, measured in volts, is the ratio of electric energy to amount of electric? charge if you comb your hair and the comb becomes positively charged,then your hair becomes? negatively charges a difference between electrical forces and gravitational forces is that gravitational forces are not affected by? repulsive interaction every proton in the universe is surrounded by its own? electric field and gravitational field a negatively charged rod is held near a metal can that rests on a dry wood table. if you touch the opposite side of the can momentarily with your finger, the can is then? positively charged the direction of an electric field is the direction of the force that the field would exert on? a proton if u use 10j of work to push a Coulomb if charge into an electric field,it's voltage with respect to its starting position? 10 V Assume that 10 J of work is needed to push a hate,at rest,into an electric field. After the charge is released there, it flies back to its starting position and its kinetic energy there will be? 10 J An electroscope is charged positively as shown by foil leaves that stand apart. as a negative charge us brought close to the electroscope, the leaves? fall closer together change carries in metal are electrons rather than protons because electrons are? loosely bound normally a small part balloon charged to several thousand volts will have a relatively small amount of? charge and energy you can touch a 100,000 volt van de graffiti generator with little harm because although voltage is high, the relatively small amount of charge means there is a relatively small amount of? energy two charges separated by one meter exert 1-N forces on each other. if the magnitude of each charge is doubled, the force on each charge is? 16 N two charges separated by one meter exert 1-N forces on each other. if the charges are pulled to 3 m separation distance, the force on each charge will be? 0.11 N two charges separated by one meter exert 1-N forces on each other. if the magnitude of each charge us doubled, the force on each charge is? 4 N two charged particles held close to each other are released. as they move, the force on each particle increases. Therefore, the particles must have? opposite signs a proton and an electro are placed in an electric field which undergoes the greater acceleration? electron What is the Law of Universal Gravitation? Fg= Gm1M2/d2 What is Coulomb's Law? FE = kq1q2/d2 How is electrical and gravitational forces alike? -Both rely on the distance -Both can attract How is electrical and gravitational force different? -Gravity cannot repel, but electrical force can -Nuclear forces are stronger than gravitational forces. What is the fundamental rule? Opposites attract, likes repel Why isn't all matter clumping up into a big ball or flying away if FE is so strong? Positive and negative particles combine together in "neutral" clumps: atoms, molecules, planets What is the most ordinary negative particle? Electron What is the most ordinary positive particle? Proton What do protons and electrons combine with to make? They combine with Neutrons to create atoms How do you change and objects charge? Take away electrons (make it positive) Add Electrons (make it negative) Can you move charge from one object to another? yes What is the Conservation of charge? you cannot create or destroy charge. When electrons in the outer shell aren't confined to a particular atom - they are free to move around in the material. Conductor When electrons are bound tightly to specific atoms Insulator What is a better conductor Metal or Glass? Metal During charging are electrons created or destroyed? No, they are transferred ( conservation of charge ) When a charge is quantized that means what? that it comes in a certain size Redistributing of electric charges in and on objects caused by the electrical influence of a charged object close by but not in contact. Charging by induction What is the lightning rod an example of? Charging by Induction When a charged object is brought near, the charges within atoms and molecules rearrange around their fixed positions Electric Polarization Act between things that are not in contact with each other. Electric Field How do forces act on things not in contact with one another? They actually alter the property of space around them by creating a force field Gravitational Field Altered space around a massive object Electric Field Altered space around an electrically charged object What two things do electric fields have? Strength and Direction Through Arrows show the direction of the field and shows the fields magnitude(strength). Vectors arrows show direction, strength is indicated by how close together the lines are Field Lines/Lines of force What are some differences between Electric and Gravitational Forces? Electric is stronger, and can attract and repel What are some differences between Electric Fields and Gravitational Fields? Electric Fields can be shielded or blocked. Electric Fields can be shielded. But why? Because there are repulsive forces available to cancel out attractive ones. Charges tend to collect where on conductors? At the points What is the Primary purpose of the lightning rod? to prevent a fire caused by lightning What is an example of a thing for which it is convenient to know its potential even when there are no charges in its field? Battery What is the Electric potential equation? V=PE/Charge A charges PE depends on its what in an electric filed? location What is it that hurts you? Its the transfer of energy, not voltage A common lab. device for producing high voltages and creating static electricity. Van de Graff Generator What are some demos we did with the Van de graff Generator? Lighting with the grounding wand pie plates and styrofoam peanuts hair and fingers 1. When the distance between two charges in halved, the electrical force between the charges... Quadruples 2. A positively charged rod is held near a metal can that rests on dry wood tablle. if you touch the opposite side of the can momentarily with your finger the can is then... Negatively charged To say that an objet is electrically polarized is to say.. its charges have been rearranged A main difference between gravitational and electric forces is that electrical forces repel or attract To say that electric charge is conserved is to say that electric charge can be neither created nor destroyed. Coulomb's Law The relationship between elctrical charge and distance; F = (k) (q1 x q2)/(d squared); If the charges are alike in sign, the force is repulsive; If the charges are unlike, the force is attractive Coulomb The SI unit of the electrical charge; One of these is equal to the total charge of 6.25x10 to the 18th power electrons Conductor Any material having free charged particles that easily flow through it when an electric force acts on them Electrostatics The study of electric charge at rest (not in motion, as in electrical currents) Conservation of Charge Electric charge is neither created nor destroyed; The total charge before an interaction equals the total charge after Insulator A material without free charged particles and through which charge does not easily flow Semiconductor A material with properties that fall between a conductor and an insulator and whose resistance can be affected by adding impurities Superconductor A material that is a perfect conductor with zero resistance to the flow of electric charge Charging by Contact Transfer of electric charge between objects by robbing or simple touching Charging by Induction Redistribution of elecftric charges in and on objects caused by the electrical influence of a charged object close by but not in contact Electrically Polarized Term applied ot an atom or molecule in which the charges are aligned so that one side has a slight excess of positive charge and the other side a slight excess of negative charge Electric Field ___ ___ = F/q; Defined as elecftric force per unit charge, it can be consided to be an "aura" surrounding charged objects and is a storehouse of electric energy; About a charged point the ____ decreases with distance according to the inversesquare law, like a gravitational field; Between oppositely charged parallel plates, the ___ ___ is uniform Electrical Potential Energy The energy a charged object possesses by virtue of its location in an electric field Electric Potential (Voltage) This is the ___ ___ energy per unit of charge; Measured in volts; ___ = (___ ___ energy)/charge Capacitor An electrical device--in its simplest form, a pair of parallel conducting plates separated by a small distance--that stores electric charge and energy Electric Force Force that one charge exerts on another; When the charges are the same sign, they repel; When the charges are opposite, they attract ... the flow of positive charge conventional current a closed loop through which charges can flow electric circuit a variable resistor or rheostat potentiometer a flow of charged particles electric current the property that determines how much current is present resistance a flow of 1 C/s ampere a circuit diagram schematic a device that measures current ammeter several voltaic cells connected together battery device designed to have a specific resistance resistor a connection that provides only one path for a current series connection a device that measure the potential difference of a circuit voltmeter a connection of two or more electric devices that provides more than one current path parallel connections a device that converts light energy to electric energy photovoltaic cell 1000 watts of electric energy delivered continuously and used for 1 hour kilowatt-hour If two conductors at different potential differences are connected by another conductor, charges flow from the conductor with the __ potential difference to the conductor with the __ potential difference. higher, lower If two conductors, A and B, are connected by another conductor, when does the flow of charge stop? when the potential difference of all conductors is equal Batteries and generators are both sources of electric energy A(n) __ is a closed loop that consists of a charge pump connected to a device that reduces the potential energy of the flowing charges. electric circuit The potential energy lost by the charges moving through a device in a circuit is represented by __. qV A general term that could refer to a battery, photovoltaic cell, or generator in a circuit is ___. charge pump No generator is 100 percent effiecient, and the kinetic energy that is not converted to electric energy usually __. becomes thermal energy. Because q is conserved, the net charge in potential energy of the charges going completely around the circuit ___. must be zero Power measure the rate at which ___ is transferred. energy The energy carried by an electric current depends on the __ transferred and the potential difference across which it moves. charge The unit used for quantity of electric charge is the __. coulomb Thus, the rate of flow of electric charge, or __, is measured in coulombs per second. electric current One coulomb per second is a(n) ___. ampere A(n) __ is used to measure current. ammeter The __ of an electric device is found by multiplying the ___ by the current. power - potential difference The power, or energy delivered to the electric device per second, is measured in joules per second. or ___. watts if you put a glass rod between two conductors that have a potential difference between them, you will have ___. almost no current ___ is measured by placing a potential difference across two points on a conductor and measuring the current. Resistance Resistance is the ratio of the potential difference to the __. current The resistance of a conductor is measured in __. ohms One ohm is the resistance that permits a current of 1 A when a ___ 1 V is applied across the resistance. potential difference A device that has a ___ and appears to be independent of the potential difference is said to obey Ohm's law. constant resistance To reduce current, you need a large resistance in a ___. small volume Superconductors are materials that have ___ resistance. zero A space heater, a hot plate, and the heating element in a hair dryer are designed to convert almost all the electric energy into ___. thermal energy Household appliances that convert electric energy into thermal energy act as __ when they are in a circuit. resistors When a charge moves through a resistor, its __ is reduced. potential difference The __ dissipated in a resistor is proportional to the square of the current that passes through it and to the resistance. power A resistor gets hot because the power that cannot pass through it is changes __. from electric energy to thermal energy When power is transmitted over long distances, energy is lost as __. thermal emery To reduce the loss of energy during transmittal power over long distances, either the current or the __ must be reduced. resistance All __ have some resistance, even though the resistance is small. wires Cable of high conductivity and __ diameter are used to transmit power long distances to reduce the resistance and reduce loss of energy as thermal energy. large Current can be reduced without reducing power, by increasing the __. voltage Electric companies measure their energy sales in __. kilowatt-hour