In a magnetized substance, the domains
line up mainly in one direction.
The magnetic field strength inside a current-carrying coil will be greater if the coil encloses a
rod of iron.
If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil with twice the number of loops,
twice as much voltage is induced.
The source of all magnetism is
moving electric charge.
A wire moving at right angles to a magnetic field has NO induced voltage
None of the above choices are correct.
A step-up transformer increases
neither power or energy.
If a steady magnetic field exerts a force on a moving charge, that force is directed
at right angles to the direction of the field.
In which direction, in relation to a magnetic field, would you run a current-carrying wire so that the force on it, resulting from the field, is minimized or even made to be zero?
run the wire parallel to the magnetic field
Voltage can be induced in a wire by
changing the current in a nearby wire.
moving the wire near a magnet.
moving a magnet near the wire.
A current can be induced in a closed circuit without the use of a battery or an electrical power supply by moving the circuit through a
magnetic field.
Magnet A has twice the magnetic field strength of Magnet B and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A exerts on magnet B is
exactly 100 N.
Which of the following options can be used to generate electricity?
Change the magnetic field strength around the circuit loop.
Change the orientation of the circuit loop with respect to the magnetic field.
Move the circuit loop into and out of a magnetic field.
Which of the following expressions shows the correct relationship between 1 T (1 tesla) and other common units?
1 N/(Am)
A long, straight, current-carrying wire runs from north to south. A compass needle placed underneath the wire points with its N-pole toward the west. In what direction is the current flowing through the wire?
south to north
When there is a change in the magnetic field in a closed loop of wire
a current is created in the loop of wire.
a voltage is induced in the wire.
electromagnetic induction occurs.
All of the following statements about magnetic field lines around a permanent magnet are true except which one?
Magnetic field lines appear to end at the north pole of a magnet.
Moving electric charges will interact with
an electric field or a magnetic field.
Figure 24-30 shows the end view of an electromagnet with current flowing through it. What is the direction of the magnetic field inside the loop?
into the page
A step-up transformer has a ratio of one to ten. Neglecting slight losses, if 100 W of power go into the primary coil, the power coming from the secondary coil is
100 W.
If a steady magnetic field exerts a force on a moving charge, that force is directed
at right angles to the direction of the motion.
Where is the magnitude of the magnetic field around a permanent magnet greatest?
The magnitude is greatest close to the poles.
A transformer actually transforms
voltage.
All of the following are ways to induce a voltage in a loop of wire except which one?
Move the loop parallel to a magnetic field.
A current in a long, straight wire produces a magnetic field. These magnetic field lines
form circles that go around the wire.
A microscopic magnetic region composed of a group of atoms whose magnetic fields are aligned in a common direction is called a(n) ____. In most materials, when these groups are randomly distributed, the substance will show ____ magnetism.
domain; no
A device that transforms electrical energy to mechanical energy is a
motor.
Four amperes of current exist in the primary coil of a transformer. The voltage across the primary coil is 110 V. What is the power output of the secondary coil?
440 W
Which compass needle orientation in the figure above might correctly describe the magnet's field at that point?
a (this is the one on the left pointing away and slightly up on the North side)
Outside a magnet, magnetic field lines are conventionally drawn from
north to south.
Magnetic domains normally occur in
iron
A current-carrying wire is placed between the poles of a magnet, as shown in Figure 24-33. What is the direction of the force on the wire?
downwards
An iron rod becomes magnetic when
the net spins of its electrons are in the same direction.
Which conversion process is the basic function of the electric generator
mechanical energy to electrical energy
An electric motor is very similar to
an electric generator.
Which of the following statements about Earth's magnetic field is true?
The geographic South Pole of Earth and Earth's magnetic north pole are relatively close to each other.
A device that transforms mechanical energy into electrical energy is a
generator.
When a bar magnet is thrust into a coil of copper wire, the coil tends to
repel the magnet as it enters.
A solenoid is in an upright position on a table. A counterclockwise current of electrons�when viewed from above�causes the solenoid to have a ____ magnetic pole at its bottom end. If a compass is placed at the top of the solenoid, the north pole of the co
south; repelled
The force on an electron moving in a magnetic field will be the largest when its direction is
perpendicular to the magnetic field direction.
What is the direction of the force acting on a current-carrying conductor lying in a magnetic field?
It is at right angles to both the direction of the magnetic field and the direction of the current.
Power is transmitted at high voltages because the corresponding current in the wires is
low so that overheating of the wires is minimized.
Thrust a magnet into a coil of wire and the coil
has a current in it.
becomes an electromagnet.
The output power of an ideal transformer is
equal to the input power.
Under which of the following conditions is the net magnetic force on a charged particle equal to zero?
when the particle is stationary
when the particle is not charged
when the particle is moving parallel to the magnetic field
If we think of the Earth as a magnet, its north (-seeking) pole is nearest
Australia
Transformers use ac so there will be the required
change in magnetic field for operation.
A certain transformer doubles input voltage. If the primary coil has 10 A of current, then the current in the secondary coil is
5 A
Magnetic field lines about a current-carrying wire
circle the wire in closed loops.
Which of the following situations is not true for magnets?
Unlike poles repel each other.
The voltage across the input terminals of a transformer is 110 V. The primary has 50 loops and the secondary has 25 loops. The voltage the transformer puts out is
55 V.
When two or more resistors are connected in parallel to a battery,
A) all of the given answers
B) the voltage across each resistor is the same.
C) the equivalent resistance of the combination is less than the resistance of any one of the resistors.
D) the
all of the given answers
In an ac circuit, the electric field
changes magnitude and direction with time
In the circuit shown below, which bulb, when burned out, will cause all other bulbs to stop glowing?
Light bulb A
Heat a copper wire and its electric resistance
increases
The number of electrons delivered daily to an average American home by an average power utility in the mid 1980s was
zero
A circuit breaker often serves the same purpose as a
fuse
A short piece of metal that melts when a large current passes through it is a:
fuse
Electrons are made to flow in a wire when there is
a potential difference across its ends
The ratio of the potential difference across a metallic conductor to the current in the conductor is known as
resistance
An automatic switch that opens when the current reaches a set value is called:
circuit breaker
When resistors are connected in parallel, we can be certain that
the potential difference across each is the same
When we say an appliance "uses up electricity," we really are saying that
electron kinetic energy is changed into heat
Stretch a copper wire so that it is thinner and the resistance between its ends
increases
Three resistors with values of R1, R2, and R3 are connected in series. What is an expression for the total resistance, Req, of the three resistors?
Req= R1+R2+R3
In a series circuit, each circuit element has the same:
current
If a resistor is added to a parallel circuit, the equivalent resistance:
decreases
A circuit has a continuous path through which charge can flow from a voltage source to a device that uses electrical energy. What is the name of this type of circuit?
a closed circuit
If a resistor is added to a series circuit, the equivalent resistance:
increases
Which set of information will allow you to calculate the kilowatt�hr usage?
the resistance, the current, and the time the circuit operates
A circuit is powered with a battery. Charge flows
through both the battery and the rest of the circuit
The primary source of electrons in an ordinary electrical circuit is
the electrical circuit itself
You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. Which statement is correct?
The 50-W bulb glows more brightly than the 100-W bulb
Which of the following does not affect a material's resistance?
Ohm's Law
Electrons move in an electrical circuit
by interacting with an established electric field
An ampere is a unit of electrical
current
Three resistors connected in parallel carry currents labeled I1, I2, and I3. What is an expression for the total current Ieq in the combined system?
It= I1+I2+I3
As more resistors are added in parallel to a constant voltage source, the power supplied by the source
increases
The source of electrons lighting an incandescent ac light bulb is
atoms in the light bulb filament
Which statement is correct?
Charge flows in a closed circuit
On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in
series
Three identical resistors are connected in series to a battery. If the current of 12 A flows from the battery, how much current flows through any one of the resistors?
12 A
As more resistors are added in series to a constant voltage source, the power supplied by the source
decreases
As more resistors are added in series to a constant voltage source, the power supplied by the source
A) the total voltage across the combination is the algebraic sum of the voltages across the individual resistors.
B) the equivalent resistance of the comb
all of the given answers
Three identical resistors are connected in series to a 12-V battery. What is the voltage across any one of the resistors?
4 V
In an electric circuit, the safety fuse is connected to the circuit in
series
The lamps in a string of Christmas tree lights are connected in parallel. What happens if one lamp burns out? (Assume negligible resistance in the wires leading to the lamps.)
The brightness of the lamps will not change appreciably
Alternating current is normally produced by a
generator
Three identical resistors are connected in parallel to a battery. If the current of 12 A flows from the battery, how much current flows through any one of the resistors?
4 A
When resistors are connected in series,
the current flowing in each is the same
Which of the following wires would have the least resistance, assuming that all of the wires have the same cross-sectional area?
a copper wire 5 cm in length
The number of current paths in a series circuit is:
one
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
Is it possible for two negative charges to attract each other?
No, they will never attract
One electron-volt corresponds to
1.6 � 10^-19J
The electrical force between charges is strongest when the charges are
close together
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
A) None of the above choices are correct.
B) half as much.
C) four times as much.
D) the same.
E) twice as
A) None of the above
A surface on which all points are at the same potential is referred to as
an equipotential surface
When a conducting sphere is charged positively, initially the charge is deposited on the left side. However, due to the sphere's conducting nature, the charge spreads uniformly throughout the surface of the sphere. Charge is uniformly distributed because:
excess electrons within the sphere move toward excess protons
Electric field lines near positive point charges
radiate outward
A positive ion has more
protons than electrons
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
16 N
A small charged ball is accelerated from rest to a speed v by a 500 V potential difference. If the potential difference is changed to 2000 V, what will the new speed of the ball be?
2v
Is it possible to have a zero electric field value between two positive charges along the line joining the two charges?
Yes, regardless of the magnitude of the two charges
A main difference between gravitational and electric forces is that electrical forces
repel or attract
For an electron moving in a direction opposite to the electric field
its potential energy decreases and its electric potential increases
Which force binds atoms together to form molecules?
electrical
Strip electrons from an atom and the atom becomes a
positive ion
The electrical force between charges depends only on the the charges
magnitude and separation distance
A neutral atom always has
the same number of protons as electrons
Which of the following materials is the best conductor of electricity?
wet skin
At twice the distance from a point charge, the strength of the electric field
is one-fourth its original value
Electric potential, measured in volts, is the ratio of electric energy to amount of electric
charge
To say that an object is electrically polarized is to say
its charges have been rearranged
The electron-volt is a unit of
energy
Several electrons are placed on a hollow conducting sphere. They
become uniformly distributed on the sphere's outer surface
Which of the following is not a vector?
electric potential
Which of the following is not a vector?
electric charge
The model of the atom shows a
nucleus consisting of both protons and neutrons, surrounded by a cloud of electrons
How can a negatively charged rod charge an electroscope positively?
by induction
A negative charge is moved from point A to point B along an equipotential surface.
No work is required to move the negative charge from point A to point B
To say that electric charge is conserved is to say that electric charge
can be neither created nor destroyed
An electron and a proton
attract each other
A conductor differs from an insulator in that a conductor
A) has more energy than an insulator.
B) has more protons than electrons.
C) none of these
D) has more electrons than protons.
E) has faster moving molecules.
none of these
When two bodies are charged, the total charge before and after charging remains the same because of:
conservation of charges
Sphere A carries a net positive charge, and sphere B is neutral. They are placed near each other on an insulated table. Sphere B is briefly touched with a wire that is grounded. Which statement is correct?
Sphere B is now negatively charged
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
fall closer together
In the circuit shown below, which bulb, when burned out, will cause all other bulbs to stop glowing?
Light bulb A
For a proton moving in the direction of the electric field
its potential energy decreases and its electric potential decreases
If a solid metal sphere and a hollow metal sphere of equal diameters are each given the same charge, the electric field (E) midway between the center and the surface is
zero for both
The absolute potential at a distance of 2.0 m from a positive point charge is 100 V. What is the absolute potential 4.0 m away from the same point charge?
50 V
The electric field inside the dome of a Van de Graaff generator
A) depends on the amount of charge the outside of dome.
B) Choices A and B are both correct.
C) depends on the volume of the dome
D) None of the other choices are correct..
None of the choices are correct
Every proton in the universe is surrounded by its own
electrica and gravitational field
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
energy
Three rods of different materials P, Q, and R, are charged by various methods. When the rods are brought near each other, the rods P and Q repel each other, while the rods P and R attract each other.
Which of the following could be the signs of the charge
- - +
A negatively charged balloon sticks to a wooden door. However, an uncharged balloon does not stick to a wooden door. What is the nature of the charge on the wooden door?
Electrically neutral
A negatively charged rod is brought near one end of an uncharged metal bar. The end of the metal bar farthest from the charged rod will be charged
negative
A solid block of metal in electrostatic equilibrium is placed in a uniform electric field. Give a statement concerning the electric field in the block's interior.
There is no electric field in the block's interior
The electric field shown
increases to the right
Is it possible to have a zero electric field value between a negative and positive charge along the line joining the two charges?
No, a zero electric field cannot exist between the two charges
When a car is struck by lightning, the resulting electric field inside the car is
zero
What are the units of the Coulomb constant k, which appears in Coulomb's law?
Nm^2/C^2
Materials in which the electrons are bound very loosely to the nuclei and can move about freely within the material are referred to as
conductors
Charge carriers in a metal are electrons rather than protons because electrons are
loosely bound
Two protons attract each other gravitationally and repel each other electrically. By far the greater force is
the electrical repulsion
The energy acquired by a particle carrying a charge equal to that on the electron as a result of moving through a potential difference of one volt is referred to as
an electron-volt
Which of the following statements is true about electric forces?
Electric forces cause objects to repel or attract each other
An atom has more electrons than protons. The atom is
a negative ion
An uncharged pith ball is suspended by a nylon fiber. When a negatively charged rubber rod is brought nearby, without touching it, the pith ball
becomes polarized
A balloon will stick to a wooden wall if the balloon is charged
either positively or negatively
Particle A has twice the charge of nearby particle B. Compared to the force on Particle A, the force on Particle B is
the same
To say that electric charge is quantized is to say that the charge on an object
is a whole-number multiple of the charge of one electron
One joule per coulomb is a
volt
Electrons are made to flow in a wire when there is
a potential difference across its ends
A cubic block of aluminum rests on a wooden table in a region where a uniform electric field is directed straight upward. What can be said concerning the charge on the block's top surface?
The top surface is charged positively
Two charges are separated by a distance d and exert mutual attractive forces of F on each other. If the charges are separated by a distance of d/3, what are the new mutual forces?
9F
The unit of electric charge, the coulomb, is the charge on
a specific large number of electrons
Is it possible for a positive and a negative charge to attract each other?
Yes, they always attract
Electric dipoles always consist of two charges that are
equal in magnitude; opposite in sign
In an electrically neutral atom the number of protons in the nucleus is equal to the number of
electrons that surround the nucleus
The direction of an electric field is the direction of the force that the field would exert on
a proton
Two charged objects are separated by a distance d. The first charge is larger in magnitude than the second charge.
The charges exert forces on each other equal in magnitude and opposite in direction