Physics Chapter 22, Physics Final

*either positively or negatively.* This is because the balloon was first charged, and was able to induce an opposite surface charge on the wall.

A balloon will stick to a wooden wall if the balloon is charged negatively. positively. either positively or negatively. None of the above choices are correct.

*none of these* Something is a conductor when it's atoms have loose electrons in in their outer shell Something is a good insulator when the electrons of their outer shell are tightly bound.

A conductor differs from an insulator in that a conductor has more energy than an insulator. has faster moving molecules. has more protons than electrons. has more electrons than protons. none of these

Semiconductor

A device composed of material not only with properties that fall between a conductor and an insulator but with resistance that changes abruptly when other conditions change, such as temperature, voltage, and electric or magnetic fields.

*repel or attract.* Gravity only attracts

A main difference between gravitational and electric forces is that electrical forces attract. are weaker. obey the inverse-square law. repel or attract. act over shorter distances.

Superconductor

A material that is a perfect conductor with zero resistance to the flow of electric charge.

Insulator

A material without free charged particles and through which charge does not easily flow.

*protons than electrons.* protons of the nucleus, which have a positive charge, determine the properties of an atom. If electrons, which are negatively charged. are removed or added to that atom it gains a charge making it an ion. If an atom has the same number of electrons as protons then it has a zero net charge.

A positive ion has more protons than neutrons. electrons than neutrons. protons than electrons. electrons than protons. neutrons than protons.

In what way are magnetic poles very different from electric charges?

All magnets have both south and north poles. Electric charges can exist as singular entities.

When do cosmic rays penetrate your body?

All the time

What is a galvanometer called when it has been calibrated to read current? When it has been calibrated to read voltage?

Ammeter, voltmeter

How does a galvanometer detect electric current?

An electric current flows through a wire in a magnetic field. The deflection force on the wire acts against a spring. The compression of the spring is proportional to current.

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.

*attract each other*

An electron and a proton attract each other. neither attract nor repel each other. repel each other.

*fall closer together.* The leaves like the rest of the device get the same charge, and cause both leaves to repel each other.

An electroscope is charged positively as shown by foil leaves that stand apart. As a negative charge is brought close to the electroscope, the leaves spread apart further. fall closer together. do not move.

Conductor

Any material having free charged particles that easily flow through it when an electric force acts on them.

*10 J.*

Assume that 10 J of work is needed to push a charge, 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 zero. 10 J. more than 10 J. 5 J. impossible to predict without additional information.

Which of the following are creatures that are known to harbor tiny magnets within their bodies?

Bacteria, pigeons, bees, wasps, monarch butterflies, and sea turtle

*loosely bound.* protons of the nucleus, which have a positive charge, determine the properties of an atom. If electrons, which are negatively charged. are removed or added to that atom it gains a charge making it an ion. If an atom has the same number of electrons as protons then it has a zero net charge.

Charge carriers in a metal are electrons rather than protons because electrons are negative. loosely bound. smaller. all of these none of these

What is a magnetic domain?

Clusters of atoms with their magnetic fields aligned

Why are the magnetic fields of superconducting magnets often stronger than those of conventional magnets?

Conventional magnets based on iron have a maximum magnetization that occurs when all of the domains are aligned. This saturation magnetization is weaker than the magnetic field of superconducting coils.

Electric field

Defined as force per unit charge, it can be considered to be an "aura" surrounding charged objects and is a storehouse of electric energy. About a charged point, the field decreases with distance according to the inverse-square law, like a gravitational field. Between oppositely charged parallel plates, the electric field is uniform.

Conservation of charge

Electric charge is neither created nor destroyed. The total charge before an interaction equals the total charge after.

What produces a magnetic field?

Electric charges in motion

What is the source of the magnetic force?

Electric charges in motion are the sources of magnetic forces.

*charge.* Volts= Joules / Coulombs or Force = energy /charge

Electric potential, measured in volts, is the ratio of electric energy to amount of electric voltage. current. charge. resistance. None of the above choices are correct.

*volts* joules: is the unit for electric potential energy coulombs: is the unit for charge conduction:The process by which heat or electricity is directly transmitted through a substance when there is a difference of temperature or of electrical potential between adjoining regions, without movement of the material.

Electric potential, unlike electric potential energy, is measured in units of _______. coulombs volts conduction joules

Electricity

General term for electrical phenomena, much like gravity has to do with gravitational phenomena, or sociology with social phenomena.

How is the magnetic force on a particle moving in a magnetic field different from gravitational and electric forces

Gravitational and electric forces act along the line connecting two interacting objects, whereas magnetic forces are perpendicular to the motion of the particle and the magnetic field.

By whom, and in what setting, was the relationship between electricity and magnetism discovered?

Hans Christian Oersted in a classroom demonstration

*positively charged* Since electrons are negatively charged, removing electrons from at atom causes the atom to become positively charged.

If the atoms of one object (initially neutral) have electrons rubbed off through friction with a second object, the first object becomes ________. positively charged negatively charged neutral in charge It's impossible to say.

*decreases by a factor of 4* The electric force gets weaker when the distance increases. Review Lesson 1 in the tutorial for additional help Just like gravity, the electric force is inversely proportional to the square of the distance between the particles.

If the distance between two charged objects is doubled, the resulting electric force on each object __________. increases by a factor of 2 increases by a factor of 4 decreases by a factor of 2 decreases by a factor of 4

*electrons that surround the nucleus.* neutrons of the nucleus, which have a positive charge, determine the properties of an atom. If electrons, which are negatively charged. are removed or added to that atom it gains a charge making it an ion. If an atom has the same number of electrons as protons then it has a zero net charge.

In an electrically neutral atom the number of protons in the nucleus is equal to the number of neutrons in the nucleus. electrons that surround the nucleus. Choices A and B are both correct. Choices A and B are both incorrect.

At the micro level, what is the difference between an unmagnetized iron nail and a magnetized iron nail?

In an unmagnetized nail, the magnetic domains have a random orientation so that the net magnetism adds to zero. In a magnetized nail, many of the magnetic domains are aligned.

*wood* Because Iron. aluminum. steel are good conductors and can ground the transfer of electrons to the ground.

In the unlikely case of a lightning strike, it is worse to be inside a building framed with iron. aluminum. steel. wood.

*upward* The horizontal components of the electric fields due to each of the two charges exactly cancel out (since the cross is directly above the midpoint), so only the vertical components add up.

In what direction is the electric field at the location depicted by the red cross in the figure?

What effect does Earth's magnetic field have on the intensity of cosmic rays striking Earth's surface?

It reduces the intensity.

How often is current reversed in the loops of a simple dc electric motor?

It reverses twice each cycle.

How is the rule for the interaction between magnetic poles similar to the rule for the interaction between electrically charged particles?

Like poles repel, unlike poles attract, and the force is proportional to the inverse square of the distance between two poles.

*charge and energy.*

Normally a small party balloon charged to several thousand volts will have a relatively small amount of charge. charge and energy. energy. neither charge nor energy.

*Both objects must be charged, either both negatively or both positively.* Like charges are repelled by each other; it is impossible to determine whether both objects are negatively charged or positively charged based on the information given.

Object A and object B are both hanging by a string, as shown in the figure. Which statement must be true? Both objects must be positively charged. Object A and object B must have the same net charge. Object A and object B must have opposite charges. Both objects must be charged, either both negatively or both positively. More than one of the above statements are true.

*They would be attracted to each other.* Since one object is attracted to object A and one object is repelled by object A, either object B is positively charged and object C is negatively charged, or visa versa.

Object A is attracted to object B and repelled by object C. All three objects are charged. What would happen if object B and object C were brought together? They would be attracted to each other. They would be repelled by each other. They would be neither repelled nor attracted to each other.

*the same.* This follows newton's 3d laws with every action there is an equal and opposite reaction.

Particle A has twice the charge of nearby particle B. Compared to the force on Particle A, the force on Particle B is four times as much. half as much. twice as much. the same. None of the above choices are correct.

In what direction relative to a magnetic field does a charged particle move in order to experience maximum deflecting force? To experience minimum deflecting force?

Perpendicular for maximum force, parallel for minimum force

Charging by induction

Redistribution of electric charges in and on objects caused by the electrical influence of a charged object close by but not in contact.

What two kinds of motion do electrons in an atom appear to have?

Revolution and spin

*negatively charged.* It becomes negatively charged because the the question say "rub electrons *from*" meaning when the comb move through your hair, it took electrons from the your hair and transferred them to the comb making the atoms on it more negative.

Rub electrons from your hair with a comb and the comb becomes positively charged. discharged. negatively charged.

*positive ion.* An atom's protons are usually constant, and if are changed for some reason, will in turn change the element of the atom. So while the nucleus of an atom usually stays constant, the electrons can come and go depending on the outer shell of the location of electrons in it, and can cause the atom to become a negative ion if it gains 1 or more electrons, or a positive ion if it loses one or more electrons.

Strip electrons from an atom and the atom becomes a negative ion. different element. positive ion. molecule.

Electrically polarized

Term applied to 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.

What is the cause of the aurora borealis (the northern lights)?

The Earth's magnetic field guides trapped charged particles to follow field lines toward the poles, where they collide with the atmosphere, causing a glow.

Coulomb

The SI unit of electrical charge. One coulomb (symbol C) is equal to the total charge of 6.25 × 10¹⁸ electrons.

*electrons* The outer electrons of atoms of certain materials are very weakly bonded, so they can easily be ripped off and transferred to other materials.

The basic reason why things become electrically charged is that the atoms (or molecules) of some materials hold on to their _______ better than those of other materials. electrons protons neutrons

Why are there probably no permanently aligned magnetic domains in Earth's core?

The core is too hot to allow atoms to maintain a constant magnetic orientation.

*a proton.*

The direction of an electric field is the direction of the force that the field would exert on an electron. an atom. a proton. a molecule. a neutral test charge.

*None of the above choices are correct.* Its 4 times less, due to the inverse square law

The electric field around an isolated electron has a certain strength 1 cm from the electron. The electric field strength 2 cm from the electron is the same. four times as much. half as much. twice as much. None of the above choices are correct.

*None of the above choices are correct.*

The electric field inside the dome of a Van de Graaff generator depends on the volume of the dome depends on the amount of charge the outside of dome. Choices A and B are both correct. None of the above choices are correct.

Electric potential

The electric potential energy per unit of charge, measured in volts, and often called *voltage: Voltage = electric potential energy/amount of charge*

*magnitude and separation distance.* According to F=k q1*q2/d2 force is directly proportional to the charged bodies (magnitude) and inversely proportional to the distance between them.

The electrical force between charges depends only on the charges' separation distance. magnitude. magnitude and separation distance. None of the above choices are correct.

*close together.* just like gravity the electric field works works off the inverse square law. It decreases inversely as the square of the distance between the two charged objects are increased.

The electrical force between charges is strongest when the charges are close together. far apart. The electric force is constant everywhere.

Why does a piece of iron in a current-carrying loop increase the magnetic field strength?

The electromagnetic field of the current-carrying loop is amplified because it aligns the domains in the iron.

Electric potential energy

The energy a charged object possesses by virtue of its location in an electric field.

How does magnetic field strength relate to the closeness of magnetic field lines about a bar magnet?

The field strength is stronger where the field lines are closer.

*electrical.* Atoms bond with each other by reacting to each other's *electrons* of their outer shells, (outer orbital) .

The fundamental force underlying all chemical reactions is electrical. centripetal. nuclear. gravitational. None of the above choices are correct.

In Chapter 22, we learned that the direction of the electric field about a point charge is radial to the charge. What is the direction of the magnetic field surrounding a current-carrying wire?

The magnetic field is directed along concentric circles surrounding the wire.

Why is the magnetic field strength greater inside a current-carrying loop of wire than about a straight section of wire

The magnetic field of each segment of wire in the loop, due to electrons moving in the wire, adds together inside the loop, thereby making the field become bunched-up.

What happens to the direction of the magnetic field about an electric current when the direction of the current is reversed

The magnetic field reverses direction at every point. A clockwise pattern of concentric circles becomes a counterclockwise pattern of concentric circles and vice versa.

Why is iron magnetic and wood not?

The magnetic fields of individual iron atoms are strong enough to align the magnetic fields of neighbor atoms. The atoms in wood have much weaker magnetic fields.

What are magnetic pole reversals?

The poles of the Earth's magnetic field undergo reversals.

Coulomb's law

The relationship between electrical force, charge, and distance: F = k · q₁q₂/d² If the charges are alike in sign, the force is repulsive; if the charges are unlike, the force is attractive.

Electrostatics

The study of electric charge at rest (not in motion, as in electric currents).

*a specific large number of electrons.* The unit of electric charge, the coulomb, 1C is the charge associated with 6.25×10⁶ electrons

The unit of electric charge, the coulomb, is the charge on a specific large number of electrons. a quark. a specific number of neutrons. one electron. a neutron.

What relative direction between a magnetic field and a current-carrying wire results in the greatest force?

The wire should be perpendicular to the field.

The force between electrically charged particles depends on the magnitude of each charge, their separation distance, and what else?

Their motion

*its charges have been rearranged.* an object that is polarized has, does not have any free electron to migrate in or out of it. due to the high conduction of the material. But instead it rearranges the atoms so that it has more positive or negative charges at one part of itself.

To say that an object is electrically polarized is to say it is electrically charged. its charges have been rearranged. it is to some degree magnetic. it is only partially conducting. its internal electric field is zero.

*can be neither created nor destroyed.* This means when electrons are transferred during a charge, no electrons are created or destroyed.

To say that electric charge is conserved is to say that electric charge may occur in an infinite variety of quantities. can be neither created nor destroyed. is a whole number multiple of the charge of one electron. will interact with neighboring electric charges. is sometimes negative.

*net charge has been created or destroyed.* This means when electrons are transferred during a charge, no electrons are created or destroyed.

To say that electric charge is conserved means that no case has ever been found where the net amount of negative charges on an object is unbalanced by positive charge on another object. total amount of charge on an object has increased. net charge has been created or destroyed. total charge on an object has changed. None of the above choices are correct.

Charging by contact

Transfer of electric charge between objects by rubbing or simple touching.

*0.11 N.* according to the inverse square law 1/3 =1/3 1/3 squared= .11

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 N. 0.11 N. 9 N. 0.33 N. 3 N.

*16 N.* 4 squared = 16 according to the inverse square law

Two charges separated by one meter exert 1-N forces on each other. If the charges are pushed to 1/4 meter separation, the force on each charge will be 2 N. 8 N. 4 N. 1 N. 16 N.

Why will dropping an iron magnet on a concrete sidewalk make it a weaker magnet?

Vibrations provide energy to randomize the magnetic directions of the domains.

*Electrons were removed.* Removing an electron causes the atom to have more protons, which have a positive charge, than electrons, which have a negative charge.

What causes an atom to become positively charged? Protons were added. Electrons were removed. Either protons were added, or electrons were removed. Electrons were added.

*The lamp does not light up because there is no voltage difference applied across it.*

What happens to a lamp when you take both ends of the wire connected to it and hold them to the same side of the 12-volt terminal of battery, and why? The lamp lights up because voltage is applied to it. The lamp does not light up because there is no voltage difference applied across it. The lamp does not light up, because there is no voltage applied to it. The lamp lights up because a voltage difference is applied to it.

*The lamp lights up because there is a voltage difference applied to it.*

What happens when you have a voltage difference between the two ends of the lamp, and why? The lamp lights up because voltage is applied to it. The lamp does not light up, because there is no voltage applied to it. The lamp lights up because there is a voltage difference applied to it.

*voltage difference between the two ends of a wire*

What is the flow of current proportional to? voltage at one end of the wire voltages at both ends of the wire voltage difference between the two ends of a wire

*Some electrons in conductors are weakly attached to the atoms, and all electrons in insulators are strongly attached to the atoms.* A small electric field within the conductor causes the electrons to drift through the material, conducting electricity. Since conductors have electrons have electrons that are weakly attached it causes more electrons to drift away or to the conductor,

What is the main difference between a conductor, such as copper, and an insulator, such as plastic? Conductors are charged, and insulators are neutral. Some electrons in conductors are weakly attached to the atoms, and all electrons in insulators are strongly attached to the atoms. Conductors have more excess electrons than insulators.

*quadruples.* according to F=k q1*q2/d2 distance is squared and the closer the charged objects are the higher the electrical force, according the the inverse square rule.

When the distance between two charges is halved, the electrical force between the charges is reduced by 1/4. quadruples. doubles. halves. None of the above choices are correct.

*electrical* Atoms bond with each other by reacting to each other's *electrons* of their outer shells, (outer orbital) .

Which force binds atoms together to form molecules? centripetal gravitational electrical nuclear none of these

Is it correct to say that an electric motor extends the physics that underlies a galvanometer? Why?

Yes. The deflection forces are the same, but the direction of current in the motor is reversed cyclically

*energy.*

You can touch a 100,000-volt Van de Graaff generator with little harm because although the voltage is high, the relatively small amount of charge means there is a relatively small amount of conduction. polarization. energy. electric field.