MMMMMMMMMM
When current is flowing in an ordinary metal wire, the magnitude of the average velocity of the electrons is closest to
1 mm/s
For an electromagnetic wave in free space having an electric field of amplitude E and a magnetic field of amplitude B, the ratio of B/E is equal to
1/c
A kilowatt-hour is equivalent to
3,600,000 J
The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity. What is the potential (relative to infinity) at a distance of 2 m from the same charge?
400 V
Which one of the arrows shown in the figure best represents the direction of the electric field between the two uniformly charged metal plates?
A
Three equal charges +Q are at three of the corners of a square of side d. A fourth charge +Q of equal magnitude is at the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square?
B
Identical light bulbs can be attached to identical ideal batteries in three different ways (A, B, or C), as shown in the figure. The ranking (from lowest to highest) of the total power produced by the battery is
B,A,C
An ideal solenoid has a self-inductance L. If you now double its radius and its length, but do not change the number of coils, what will its self-inductance be?
L/2
The wire in the figure carries a steady current I. What is true about the currents induced in each of the three loops shown? The wire and the three loops are all in the same plane.
No current is induced in any loop.
Three identical capacitors are connected in series across a potential source (battery). If a charge of Q flows into this combination of capacitors, how much charge does each capacitor carry?
Q
The figure shows conventional current passing through a resistor. The arrow shows the direction 8) in which this conventional current is flowing. Which of the following statements are correct? (There could be more than one correct choice.)
The electric potential is lower at point b than at point a,,,The current at point b is the same as the current at point a
A region of space contains a uniform electric field, directed toward the right, as shown in the figure. Which statement about this situation is correct?
The potential at points A and B are equal, and the potential at point C is lower than the potential at point A.
An object is hung using a metal spring. If now a current is passed through the spring, what will happen to this system?
The spring will contract, raising the weight.
Consider two copper wires of equal length. One wire has twice the cross -sectional area of the other. How do the resistances of these two wires compare
The thicker wire has one -half the resistance of the thinner wire
Which one of the following types of electromagnetic wave travels through space the fastest?
They all travel through space at the same speed.
An inductor stores energy in its magnetic field.
True
Which one of the following statements is correct?
When a current-carrying wire is in your right hand, with your thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.
As shown in the figure, a metal bar is in contact with a pair of parallel rails. A steady, uniform, magnetic field B is present directed to the right. The bar is moving upward with velocity of magnitude Α. What is the polarity of the induced emf in terminals X and Y?
X and Y are at the same potential.
If a calculated quantity has units of (N·s)/(C*m),that quantity could be
a magnetic field
If the voltage across a circuit of constant resistance is doubled, the power dissipated by that circuit will
be four times as large
As a proton moves in a direction perpendicular to the electric field lines
both its electric potential and electric potential energy remain constant.
Which of the following changes will increase the capacitance of a parallel-plate capacitor?
decrease the separation between the plates. introduce a dielectric material between the plates
If the electric field between the plates of a given air-filled capacitor is weakened by removing charge from the plates, the capacitance of that capacitor
does not change
The electron-volt is a unit of
energy.
As shown in the figure, two solenoids are side by side. The switch S is initially open. When S is suddenly closed, the direction of the induced current through the resistor R is
from b to a.
A transformer is a device used to
increase or decrease an ac voltage.
When a ferromagnetic material is placed in an external magnetic field, the net magnetic field of its magnetic domains becomes
larger.
When a current flows through a metal wire, the moving charges are
only electrons
A flat coil is in a uniform magnetic field. The magnetic flux through the coil is greatest when the plane of its area is
perpendicular to the magnetic field.
If a quantity you calculated has units of (kg ∙ m^2)/(s*C^2) what is that quantity
resistance
A galvanometer can be converted to an ammeter by the addition of a
small resistance in parallel
Kirchhoff's loop rule is a statement of
the law of conservation of energy.
When unequal resistors are connected in parallel in a circuit,
the potential drop is always the same across each resistor.
An electron has an initial velocity to the south but is observed to curve upward as the result of a magnetic field. This magnetic field must have a component
to the west
A long, straight, horizontal wire carries current toward the east. An electron moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the electron?
toward the south
At a particular instant, an electron moves toward the east in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it is
toward the south
A vertical wire carries a current straight up in a region where the magnetic field vector points toward the north. What is the direction of the magnetic force on this wire?
toward the west
A negatively charged particle -Q is moving to the right, directly above a wire having a current I flowing to the right, as shown in the figure. In what direction is the magnetic force exerted on the particle due to the current?
upward
A ring with a clockwise current (as viewed from above the ring) is situated with its center directly above another ring, which has a counter-clockwise current, as shown in the figure. In what direction is the net magnetic force exerted on the top ring due to the bottom ring?
upward
Inordertoconstructavoltmeterfromagalvanometer,onenormallywould
use a very large series resistor
Which of the following are units for the magnetic moment?
(N*m/t) (A*m^2)
The maximum torque on a flat current-carrying loop occurs when the angle between the plane of the loop's area and the magnetic field vector is
0
If the length and diameter of a wire of circular cross section are both tripled, the resistance will be
1/3 of what it originally was
Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually diminishes on both spheres by leaking off. When each of the spheres has lost half its initial charge, what will be the magnitude of the electrostatic force on each one?
1/4 F
An ideal parallel-plate capacitor has a capacitance of C. If the area of the plates is doubled and the distance between the plates is halved, what is the new capacitance?
4C
A resistor and an inductor are connected in series to a battery. The time constant for the circuit represents the time required for the current to reach
63% of the maximum current.
The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 µT. What is the magnetic field at a distance of 1 cm from this wire?
8 µT
Three equal positive point charges +q are placed at the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?
A
Three equal-magnitude point charges of varying signs are placed at the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?
A
Three equal negative point charges -q are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?
C
n a velocity selector consisting of perpendicular electric and magnetic fields, the speeds of the charged particles passing through the selector are increased or decreased until they are equal to the desired speed.
False
For the circuit shown in the figure, write the Kirchhoff current equation for the node labeled A. Notice the directions of the currents!
I1 - I2 + I3 = 0
You obtain a 100-W light bulb and a 50-W light bulb. Instead of connecting them in the normal cway, you devise a circuit that places them in series across normal household voltage. If each one is an incandescent bulb of fixed resistance, which statement about these bulbs is correct?
The 50-W bulb glows more brightly than the 100-W bulb.
Two very small plastic balls of equal mass are released from rest. One of them carries +10 µC of excess charge and the other one carries +1µC of charge. No other charges or fields are present. Which of the following statements are true about them as they move away from each other?
The balls always have accelerations of equal magnitude,,, The speed of the balls keeps increasing.
A conductor is placed in a steady external electric field. Which of the following statements are correct for this situation?
The electric field is zero inside the conductor. The electric field just outside the surface of the conductor is perpendicular to the surface. All the free electrons go to the surface of the conductor.
Which of the following statements about electromagnetic waves in free space are true?
The electric field vector is always at right angles to the magnetic field vector. The higher-frequency waves have shorter wavelengths than the lower-frequency waves.
A hydrogen nucleus, which has a charge +e, is situated to the left of a carbon nucleus, which has a charge +6e. Which statement is true?
The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is equal to the force exerted on the carbon nucleus.
The figure shows electrons passing through a resistor. The arrow shows the direction in which 7) the electrons are moving. Which of the following statements are correct? (There could be more than one correct choice.)
The electrons are losing electric potential energy as they move through the resistor from a to b,,,The electric potential is higher at point b than at point a,,,The speed of the electrons at point b is the same as it is at point a
Four unequal resistors are connected in a parallel with each other. Which one of the following statements is correct about this combination?
The equivalent resistance is less than that of the smallest resistor.
Four unequal resistors are connected in series with each other. Which one of the following statements is correct about this combination?
The equivalent resistance is more than the largest resistance.
Two tiny beads are 25 cm apart with no other charges or fields present. Bead A carries 10 µC of charge and bead B carries 1 µC. Which one of the following statements is true about the magnitudes of the electric forces on these beads?
The force on A is exactly equal to the force on B.
Which of the following statements about electromagnetic waves in free space are true?
The frequency of the magnetic field is the same as the frequency of the electric field. The electric field carries the same mount of energy as the magnetic field.
A coil lies flat on a tabletop in a region where the magnetic field vector points straight up. The magnetic field vanishes suddenly. When viewed from above, what is the sense of the induced current in this coil as the field fades?
The induced current flows counterclockwise
Consider two copper wires of equal cross-sectional area. One wire has 3 times the length of the other. How do the resistances of these two wires compare
The longer wire has 3 times the resistance of the shorter wire
A 9-V battery is hooked up to two resistors in series using wires of negligible resistance. One has a resistance of 5 !, and the other has a resistance of 10 !. Several locations along the circuit are marked with letters, as shown in the figure. Which statements about this circuit are true? (There could be more than one correct choice.)
The potential at B is equal to the potential at C,,,The current is exactly the same at points A, B, C, and D.
A negatively-charged rod is brought close to (but does not touch) two neutral spheres that are in contact with each other but insulated from the ground. If the two spheres are then separated, what kind of charge will be on the spheres?
The sphere near the charged rod becomes positive and the other one becomes negative
Consider two copper wires with circular cross-sections and equal lengths. One wire has 3 times the diameter of the other. How do the resistances of these two wires compare
The thicker wire has 1/9 the resistance of the thinner wire
A solid aluminum cube rests on a wooden table in a region where a uniform external electric field is directed straight upward. What can we say concerning the charge on the top surface of the cube?
The top surface is charged positively.
When two or more different capacitors are connected in series across a potential source, which of the following statements must be true? (There could be more than one correct choice.)
The total voltage across the combination is the algebraic sum of the voltages across the individual capacitors,,,The equivalent capacitance of the combination is less than the capacitance of any of the capacitors,,,Each capacitor carries the same amount of charge
Except for their color, a perfectly black (absorbing) object is identical to a perfectly white (reflecting) object. If identical light falls on both of these objects, what is true about the momentum they will receive from this light?
The white object will receive twice as much as the black object.
A proton and an electron are released from rest, with only the electrostatic force acting. Which of the following statements must be true about them as they move toward each other?
Their electric potential energy keeps decreasing. Their kinetic energy keeps increasing.
Two protons are fired toward each other in a particle accelerator, with only the electrostatic force acting. Which of the following statements must be true about them as they move closer together?
Their electric potential energy keeps increasing. Their kinetic energy keeps decreasing.
A circular wire ring is situated above a long straight wire, as shown in the figure. The straight wire has a current I flowing to the right, and this current is increasing at a constant rate. Which of the following statements is true?
There is an induced current in the wire ring, directed in clockwise orientation.
An electron and a proton are released simultaneously from rest and start moving toward each other due to their electrostatic attraction, with no other forces present. Which of the following statements are true just before they are about to collide?
They are closer to the to the initial position of the proton that to the initial position of the electron.
For the circuit shown in the figure, write the Kirchhoff loop equation for the entire outside loop. Notice the directions of the currents!
V1+I3R3-V3-I1R1=0
As shown in the figure, two solenoids are in line. The switch S, initially closed, is suddenly opened. Just after opening S, what is the polarity of the induced emf in terminals X and Y?
X is positive and Y is negative
A bar magnet is oriented above a copper ring, as shown in the figure. The magnet is dropped and passes completely through the ring. As viewed from above, what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it?
counterclockwise
A circular coil lies flat on a horizontal surface. A bar magnet is held above the center of the coil with its north pole pointing down. If the magnet is dropped from this position what is the direction of the induced current in the coil, as viewed from above?
counterclockwise
The energy density of an electromagnetic wave in free space is
equally divided between the magnetic and the electric fields.
A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field lines. Ignoring the particle's weight, the particle will
follow a circular path
As shown in the figure, two parallel wires carry a current I in opposite directions, and this current is decreasing. A rectangular loop is centered between the wires. The direction of the induced current through the resistor R is
from b to a
If the electric potential at a point in space is zero, then the electric field at that point must be
impossible to determine based on the information given.
A charged particle moves with a constant speed through a region where a uniform magnetic field is present. If the magnetic field points straight upward, the magnetic force acting on this particle will be strongest when the particle moves
in a plane parallel to Earth's surface
You buy a AA battery in the store, and it is marked 1.5 V. If this marking is strictly accurate, while this battery is fresh
its terminal voltage will be less than 1.5 V when it is used in a circuit.
A charged particle that is moving in a static uniform magnetic field
may experience a magnetic force, but its speed will not change.
A transformer is a device that normally
operates on either dc or ac.
If a quantity you calculated has units of ! ∙ m what is that quantity
potential
If a quantity you calculated has units of (kg ∙ m^2)/(s^2*C) , what is that quantity
potential
Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch?
q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2
If the primary coil of a transformer contains more loops than the secondary coil then it is a
step-down transformer.
If the secondary coil of a transformer contains more loops than the primary coil, then it is a
step-up transformer.
A 9-V battery is hooked up to two resistors in series. One has a resistance of 5 !, and the other has a resistance of 10 !. Several locations along the circuit are marked with letters, as shown in the figure. Through which resistor is energy being dissipated at the higher rate?
the 10-! resistor
When unequal resistors are connected in series across an ideal battery,
the current flowing in each is the same.
The magnetic force on a current-carrying wire in a magnetic field is the strongest when
the current is perpendicular to the magnetic field lines
Kirchhoff's junction rule is a statement of
the law of conservation of charge.
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in the same direction,
the wires pull toward each other.
Four tiny charged particles (two having a charge +Q and two having a charge -Q) are distributed on the x- and y-axes as shown in the figure. Each charge is equidistant from the origin. In which direction is the net electric field at the point P on the y-axis?
upwards and towards the left
A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage. At the moment contact is made with the battery, the voltage across the resistor is
zero.
Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane as shown in the figure. The charges are all equidistant from the origin. The amount of work required to move a positively charged particle from point P to point O (both of which are on the z-axis) is
zero.
If a calculated quantity has units of T · m/A, that quantity could be
μ0
Consider two copper wires of equal cross-sectional area. One wire has 3 times the length of the other. How do the resistivities of these two wires compare
Both wires have the same resistivity
The length of a certain wire is kept same while its radius is doubled. What is the new resistance of this wire
It is reduced by a factor of 4
The length of a certain wire is doubled and at the same time its radius is reduced by a factor of 2. What is the new resistance of this wire
It it 8 times as large
Three identical capacitors are connected in parallel to a potential source (battery). If a charge of Q flows into this combination, how much charge does each capacitor carry?
Q/3
Which statements must be true about the surface of a charged conductor in which no charge is moving?
The electric field is perpendicular to the surface. The electric potential is constant over the surface.
If the result of your calculation of a quantity has SI units kg · m2/(s2 · C), that quantity could be
an electric potential difference.
Which of the following will increase the capacitance of a parallel-plate capacitor?
an increase in the plate area and a decrease in the plate separation
If a quantity you calculated has units of A ∙ s, what is that quantity?
charge
An capacitor consists of two large parallel plates of area A separated by a very small distance d. This capacitor is connected to a battery and charged until its plates carry charges +Q and -Q, and then disconnected from the battery. If the separation between the plates is now doubled, the potential difference between the plates will
double
An ac generator consisting of a coil with N turns rotating at angular speed Ν in an external magnetic field B produces a maximum emf Ή0.If you now decrease the number of turns in the coil to N/2 and at the same time cause it to rotate twice as fast, what will be the new maximum emf if you do not change any of the other quantities?
e0
As shown in the figure, a straight wire carries a current I into the page. The wire passes through the center of a toroidal coil. If the current I is quickly reduced to zero, the direction of the induced current through the resistor R is
from b to a.
As shown in the figure, one end of a metal bar is in contact with a circular rail and the other end is pivoted at P. A steady uniform, magnetic field B into the page is present. As the bar rotates about point P in a clockwise direction, the direction of the induced current through the resistor R is
from b to a.
When the current through a resistor is increased by a factor of 4, the power dissipated by the resistor
increases by a factor of 16
Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane, as shown in the figure. These particles are all equidistant from the origin. The electric potential (relative to infinity) at point P on the z-axis due to these particles, is
zero
Which one of the following quantities is equivalent to 1 W
1V∙A
The length of a certain wire is kept same while its radius is doubled. What is the new resistivity of this wire
It does not change
A proton, moving in a uniform magnetic field, moves in a circle perpendicular to the field lines and takes time T for each circle. If the proton's speed tripled, what would now be its time to go around each circle?
T
If a quantity you calculated has units of (kg ∙ m^3)/(s*C^2) what is that quantity
resistivity
An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in the figure. Which trajectory (X, Y, Z, or W) will the electron follow in the field?
trajectory Z
A proton is accelerated from rest through a potential difference V0 and gains a speed v0. If it were accelerated instead through a potential difference of 2V0, what speed would it gain?
v0 sqrt(2)
A bar magnet is close to a solenoid, as shown in the figure. As viewed through the solenoid looking toward the magnet, what is the direction (clockwise or counterclockwise) of the current (if any) induced in the solenoid in each case?
(a) counterclockwise (b) no induced current
The figure shows four Gaussian surfaces surrounding a distribution of charges. (a) Which Gaussian surfaces have an electric flux of +qȦΉo through them? (b) Which Gaussian surfaces have no electric flux through them?
(a) surface b (b) surface c
Which one of the following expressions is the correct representation for the speed of light in vacuum?
1 /root(e0µ0)
During a period of high power demand, the voltage output of the power company is reduced by 5.0%. By what percentage is the power in a resistor decreased
10%
The potential (relative to infinity) at the midpoint of a square is 3.0 V when a point charge of +Q is located at one of the corners of the square. What is the potential (relative to infinity) at the center when each of the other corners is also contains a point charge of +Q?
12 V
At a distance d from a point charge Q, the energy density in its electric field is u. If we now go to a distance d/2 from the charge, what is the energy density at the new location?
16u
The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 µT. What is the magnetic field at a distance of 4 cm from this wire?
2 µT
Two ideal parallel-plate capacitors are identical in every respect except that one has twice the plate area of the other. If the smaller capacitor has capacitance C, the larger one has capacitance
2C
A charged particle is observed traveling in a circular path of radius R in a uniform magnetic field. If the particle were traveling twice as fast, the radius of the circular path would be
2R
A small charged plastic ball is vertically above another charged small ball in a frictionless test tube as shown in the figure. The balls are in equilibrium a distance d apart. If the charge on each ball is doubled, the equilibrium distance between the balls in the test tube would become
2d
A resistor and an inductor are connected in series to a battery. The battery is suddenly removed from the circuit and replaced by a wire to complete the circuit. The time constant for of the new circuit represents the time required for the current to decrease to
37% of the original value.
When a dielectric material is introduced between the plates of a parallel-plate capacitor and completely fills the space, the capacitance increases by a factor of 4. What is the dielectric constant of the material that was introduced?
4
When two long parallel wires carry unequal currents, the magnitude of the magnetic force that one wire exerts on the other is F. If the current in both wires is now doubled, what is the magnitude of the new magnetic force on each wire?
4F
A resistor is made out of a wire having a length L. When the ends of the wire are attached across the terminals of an ideal battery having a constant voltage V0 across its terminals, a current I flows through the wire. If the wire were cut in half, making two wires of length L/2, and both wires were attached across the terminals of the battery (the right ends of both wires attached to one terminal, and the left ends attached to the other terminal), how much current would the battery put out?
4I
A very long straight current-carrying wire produces a magnetic field of 20 mT at a distance d from the wire. To measure a field of 5 mT due to this wire, you would have to go to a distance from the wire of
4d
A coil of wire containing N turns is in an external magnetic field that is perpendicular to the plane of the coil and it steadily changing. Under these circumstances, an emf Ή is induced in the coil. If the rate of change of the magnetic field and the number of turns in the coil are now doubled (but nothing else changes), what will be the induced emf in the coil?
4e
At a distance d from a point charge Q, the energy density in its electric field is u. If we double the charge, what is the energy density at the same point?
4u
Two light beams of different frequency but the same intensity fall on a black (totally absorbing) surface, striking perpendicular to the surface. Which of the following statements are true?
Both beams exert the same pressure on the surface
A parallel-plate capacitor consists of a set of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference across the plates. A slab of a dielectric material is inserted in the region between the plates and completely fills it. What changes would you observe as the dielectric is inserted?
Both the charge on the plates of the capacitor and its capacitance would change.
Identical ideal batteries are connected in different arrangements to the same light bulb, as shown in the figure. For which arrangement will the bulb shine the brightest?
C
A 5-μF, a 7-μF, and an unknown capacitor CX are connected in series between points a and b. What do you know about the equivalent capacitance Cab between a and b ? (There could be more than one correct choice.)
Cab<CX,,,Cab<5 μF
A 5-μF, a 7-μF, and an unknown capacitor CX are connected in parallel between points a and b as shown in the figure. What do you know about the equivalent capacitance Cab between a and b ? (There could be more than one correct choice.)
Cab>12μF,,,Cab>CX
An ideal parallel-plate capacitor having circular plates of diameter D that are a distance d apart stores energy U when it is connected across a fixed potential difference. If you want to triple the amount of energy stored in this capacitor by changing only the size of its plates, the diameter should be changed to
Dsqrt(3)
Two long parallel wires are placed side-by-side on a horizontal table and carry current in the same direction. The current in one wire is 20 A, and the current in the other wire is 5 A. If the magnetic force on the 20-A wire has magnitude F, what is the magnitude of the magnetic force on the 5-A wire? No external magnetic fields are present.
F
According to Faraday's law, a coil in a strong magnetic field must have a greater induced emf in it than a coil in a weak magnetic field.
False
According to Lenz's law, the induced current in a circuit always flows to oppose the external magnetic field through the circuit.
False
According to Lenz's law, the induced current in a circuit always flows to oppose the external magnetic flux through the circuit.
False
Inductors cannot store energy because they cannot store charge.
False
Inductors store energy by accumulating excess charge within their coils
False
In the circuit shown in the figure, the resistor R has a variable resistance. As R is decreased, what happens to the currents?
I1 decreases and I2 increases.
When a certain capacitor carries charges of ±10 µC on its plates, the potential difference cross the plates is 25 V. Which of the following statements about this capacitor are true?
If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will not change. If we double the charges on the plates to ±20 µC, the potential difference across the plates will also double.
The plates of a parallel-plate capacitor are maintained with constant voltage by a battery as they are pulled apart. What happens to the strength of the electric field between the plates during this process?
It decreases
A battery charges a parallel-plate capacitor fully and then is removed. The plates are then slowly pulled apart. What happens to the potential difference between the plates as they are being separated?
It increases
The length of a certain wire is doubled and at the same time its radius is also doubled. What is the new resistance of this wire
It is 1⁄2 as large
The length of a certain wire is doubled while its radius is kept constant. What is the new resistance of this wire
It is 2 times as large
At a certain instant, coil A is in a 10-T external magnetic field and coil B is in a 1-T external magnetic field. Both coils have the same area and are oriented at right angles to the field. Which coil will have a greater emf induced in it?
It is impossible to know without more information about the fields.
Two long, parallel wires carry currents of different magnitudes. If the amount of current in one of the wires is doubled, what happens to the magnitude of the force that each wire exerts on the other?
It is increased by a factor of 2.
Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are halved and their separation is also halved, what happens to the electrical force that each charge exerts on the other one?
It remains the same
Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are doubled and their separation is also doubled, what happens to the electrical force that each charge exerts on the other one?
It remains the same.
Two long, parallel wires carry currents of different magnitudes. If the current in one of the wires is doubled and the current in the other wire is halved, what happens to the magnitude of the magnetic force that each wire exerts on the other?
It stays the same.
In outer space, a positive charge q is released near a positive fixed charge Q, as shown in the figure. As q moves away from Q, what is true about the motion of q?
It will move with decreasing acceleration,,, It will move with increasing speed
The three loops of wire shown in the figure are all hanging in the same uniform magnetic field B that is perpendicular to the page and does not vary with time. Loop 1 swings back and forth like the bob in a pendulum, Loop 2 rotates about a vertical axis, and Loop 3 oscillates up and down at the end of a spring. Which loop (or loops) will have an emf induced in them?
Loop 2
The wire in the figure carries a current I that is increasing with time at a constant rate. The wire and the three loops are all in the same plane. What is true about the currents induced in each of the three loops shown?
Loop A has clockwise current, loop B has no induced current, and loop C has counterclockwise current.
The wire in the figure carries a current I that is decreasing with time at a constant rate. The wire and the three loops are all in the same plane. What is true about the currents induced in each of the three loops shown?
Loop A has counterclockwise current, loop B has no induced current, and loop C has clockwise current.
A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held above the center of the coil with its south pole downward. The magnet and the coil are now both raised upward with the same velocities. As viewed from above, what is the direction of the current induced in the coil as the magnet approaches the coil?
No current is induced in the coil.
A resistor, an uncharged capacitor, a dc voltage source, and an open switch are all connected in series. The switch is closed at time t = 0 s. Which one of the following is a correct statement about the circuit?
Once the capacitor is essentially fully charged, there is no current in the circuit
The figure shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: (i) The charge on P is smaller than the charge on Q. (ii) The electrostatic force on P is smaller than the force on Q. Which of the above statements are true?
Only (i) is true
A particle carrying a charge of +e travels in a circular path of radius R in a uniform magnetic field. If instead the particle carried a charge of +2e, the radius of the circular path would have been
R/2
As shown in the figure, a coil of wire is placed in the xy-plane, centered on the z-axis. A solenoid is centered on the z-axis and is carrying a steady dc current. Which one of the following actions will not result induce an emf in the coil?
Rotate the coil about the z-axis
The lamps in a string of decorative lights are connected in parallel across a constant-voltage power source. 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.
When two or more different capacitors are connected in parallel across a potential source (battery), which of the following statements must be true? (There could be more than one correct choice.)
The capacitor with the largest capacitance has the most charge,,,The potential difference across each capacitor is the same.
A resistor, an uncharged capacitor, a dc voltage source, and an open switch are all connected in series. The switch is closed at time t = 0 s. Which one of the following is a correct statement about this circuit?
The charge on the capacitor after four time constants is about 98% of the maximum value.
A dielectric material such as paper is inserted between the plates of a capacitor as the capacitor holds a fixed charge on its plates. What happens to the electric field between the plates as the dielectric is inserted?
The field becomes weaker
A wire lying in the plane of this page carries a current directly toward the top of the page. What is the direction of the magnetic force this current produces on an electron that is moving perpendicular to the page and outward from it on the left side of the wire?
The force is zero.
A long straight wire has a constant current flowing to the right. A rectangular metal loop is situated above the wire, and also has a constant current flowing through it, as shown in the figure. Which one of the following statements is true?
The net magnetic force on the rectangle is downward, and the net torque on it is zero
Two protons are released from rest, with only the electrostatic force acting. Which of the following statements must be true about them as they move apart?
Their acceleration keeps decreasing. Their kinetic energy keeps increasing. Their electric potential energy keeps decreasing.
A circular coil lies flat on a horizontal surface. A bar magnet is held fixed above the center of the coil with its north pole pointing downward. What is the direction of the induced current in the coil, as viewed from above?
There is no current in the coil.
Coil A is close to, but not touching, coil B. If a steady counterclockwise 100-A current flows in coil A, what can you say about the induced current in coil B?
There will be no induced current in coil B.
The figure shows two unequal charges, +q and -Q. Charge -Q has greater magnitude than charge +q. Point X is midway between the charges. In what section of the line will there be a point where the resultant electric field is zero?
VW
X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y?
X is negative and Y is positive
As shown in the figure, a straight wire carries a steady current I. A metal bar is in contact with a pair of rails and is in upward motion with velocity of magnitude Α. The polarity of the induced emf in terminals X and Y is
Y is positive and X is negative
As shown in the figure, a C-shaped conductor is in a uniform magnetic field B out of the page, and this field is increasing. What is the polarity of the induced emf in terminals X and Y?
Y is positive and X is negative.
If the result of your calculations for a quantity has SI units of C2 · s2/(kg · m2), that quantity could be
a capacitance
If a calculated quantity has units of N/(A*M) that quantity could be
a magnetic field
Decreasing the resistance of an ammeter's shunt resistance
allows it to measure a larger current at full scale deflection
If the result of your calculation of a quantity has SI units of kg · m/(s2 · C), that quantity could be
an electric field strength.
An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d. This capacitor is connected across a battery that maintains a constant potential difference between the plates. If the separation between the plates is now doubled, the magnitude of the charge on the plates will
be cut in half
An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery that maintains a constant potential difference across the plates. If the separation between the plates is now doubled, the amount of electrical energy stored on the capacitor will
be cut in half.
If we double the resistance in a circuit but keep the current in it constant, the power dissipated by that circuit will
be two times as great
A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but four times as long. If, however, the total resistance is to remain as before, the diameter of the new wire must
be two times the original diameter
Consider an ideal solenoid of length L, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the length of the solenoid becomes twice as long (to 2L), but all other quantities remained the same, the magnetic field inside the solenoid will
become one-half as strong as initially.
When a current flows through an ionic liquid such as salty water, the moving charges are
both positive and negative ions
A negatively-charged particle moves across a constant uniform magnetic field that is perpendicular to the velocity of the particle. The magnetic force on this particle
causes the particle to accelerate
A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current
circles the wire in a counter-clockwise direction
A bar magnet is oriented above a copper ring, as shown in the figure. If the magnet is kept fixed while the ring is dropped, what is the direction of the current induced in the ring, as viewed from below the ring?
clockwise
A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held above the center of the coil with its south pole downward. The magnet is released from rest and falls toward the coil. As viewed from above, what is the direction of the current induced in the coil as the magnet approaches the coil?
clockwise
A coil lies flat on a horizontal tabletop in a region where the magnetic field points straight down. The magnetic field disappears suddenly. When viewed from above, what is the direction of the induced current in this coil as the field disappears?
clockwise
A coil lies flat on a level tabletop in a region where the magnetic field vector points straight up. The magnetic field suddenly grows stronger. When viewed from above, what is the direction of the induced current in this coil as the field increases?
clockwise
A bar magnet is oriented above a copper ring, as shown in the figure. If the magnet is pulled upward, what is the direction of the current induced in the ring, as viewed from above?
counterclockwise
An outer metal ring surrounds an inner metal ring, as shown in the figure. The current in the outer ring is counterclockwise and decreasing. What is the direction of the induced current in the inner ring?
counterclockwise
A long straight wire lies on a horizontal table and carries an ever-increasing current toward the north. Two coils of wire lie flat on the table, one on either side of the wire. When viewed from above, the direction of the induced current in these coils is
counterclockwise in the east coil and clockwise in the west coil.
A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire as you view it in such a way that the current is coming directly toward you?
counterclockwise, around the y-axis
If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit will
decrease to one -half its original value
Doubling the capacitance of a capacitor that is holding a constant charge causes the energy stored in that capacitor to
decrease to one-half.
As more resistors are added in series to a constant voltage source, the power supplied by the source
decreases
A wire lying in the plane of the page carries a current toward the bottom of the page, as shown in the figure. What is the direction of the magnetic force it produces on an electron that is moving to the left directly toward the wire, as shown?
directly toward the bottom of the page
An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery and charged until its plates carry charges +Q and -Q, and the battery is then disconnected. If the separation between the plates is now doubled, the electrical energy stored in the capacitor will
double
When you double the number of windings in an ideal solenoid while keeping all other parameters (radius, length and current) fixed, the magnetic field at the center of the solenoid will
double
The electric field at point P due to a point charge Q a distance R away from P has magnitude E. In order to double the magnitude of the field at P, you could
double the charge to 2Q.
For the horseshoe magnet shown in the figure, the left end is a north magnetic pole and the right end is a south magnetic pole. When the switch is closed in the circuit, which way will the wire between the poles of the horseshoe magnet initially deflect?
downward
In a certain velocity selector consisting of perpendicular electric and magnetic fields, the charged particles move toward the east, and the magnetic field is directed to the north. What direction should the electric field point?
downward
We observe that a moving charged particle experiences no magnetic force. From this we can definitely conclude that
either no magnetic field exists or the particle is moving parallel to the field
A resistor and an inductor are connected in series to an ideal battery of constant terminal voltage. At the moment contact is made with the battery, the voltage across the inductor is
equal to the battery's terminal voltage.
Gaussian surfaces A and B enclose the same positive charge +Q. The area of Gaussian surface A is three times larger than that of Gaussian surface B. The electric flux through Gaussian surface A is
equal to the flux of electric field through Gaussian surface B.
As shown in the figure, a metal bar is in contact with a pair of metal parallel rails. A steady uniform magnetic field B, perpendicular to the plane of the rails and pointing outward from the page, is present. The bar is in downward motion with velocity of magnitude Α. The direction of the induced current through the resistor R is
from a to b
As shown in the figure, a battery supplies a steady current to the solenoid on the left. The two solenoids are moving toward each other with speeds v. The direction of the induced current through the resistor R is
from a to b.
In the figure, a bar magnet moves away from the solenoid. The direction of the induced current through the resistor R is
from a to b.
Two solenoids are close to each other, as shown in the figure, with the switch S open. When the switch is suddenly closed, which way will the induced current flow through the galvanometer in the left-hand solenoid?
from right to left
A wire is carrying current vertically downward. What is the direction of the force on this wire due to Earth's magnetic field?
horizontally towards the east
Suppose you have two capacitors and want to use them to store the maximum amount of energy by connecting them across a voltage source. You should connect them
in parallel across the source.
A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the electric potential energy of the electron due to the proton
increases
A parallel-plate capacitor is connected to a battery and becomes fully charged. The capacitor is then disconnected, and the separation between the plates is increased in such a way that no charge leaks off. As the plates are being separated, the energy stored in this capacitor
increases
Over ordinary temperature ranges, the resistance of most metals such as copper
increases as the metal gets hotter
As more resistors are added in parallel across a constant voltage source, the power supplied by the source
increases.
An ideal ammeter should
introduce a very small series resistance into the circuit whose current is to be measured
A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallic sphere that is insulated from ground. It is allowed to touch the sphere for a few seconds, and then is separated from the sphere by a small distance. After the rod is separated, the rod
is repelled by the sphere.
Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at a point exactly between the two wires
is zero.
As an electron moves in the direction the electric field lines
it is moving from high potential to low potential and gaining electric potential energy.
As a proton moves in the direction the electric field lines
it is moving from high potential to low potential and losing electric potential energy.
The plates of a parallel-plate capacitor are maintained with constant potential by a battery as they are pulled apart. During this process, the amount of charge on the plates
must decrease
A long straight wire carrying a 4-A current is placed along the x-axis as shown in the figure. What is the direction of the magnetic field at a point P due to this wire?
out of the plane of the page
The direction of the force on a current-carrying wire in a magnetic field is
perpendicular to both the current and the magnetic field.
In an electromagnetic wave in free space, the electric and magnetic fields are
perpendicular to one another and perpendicular to the direction of wave propagation.
Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current directly toward you, and the wire on your left carries current directly away from you. From your point of view, the magnetic field at a point exactly midway between the two wires
points downward.
If the current flowing through a circuit of constant resistance is doubled, the power dissipated by that circuit will
quadruple in magnitude
Doubling the potential across a given capacitor causes the energy stored in that capacitor to
quadruple.
Which one of the following lists gives the correct order of the electromagnetic spectrum from low to high frequencies?
radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays
Which one of the following lists gives the correct order of the electromagnetic waves from longer wavelength to shorter wavelength?
radio waves, microwaves, infrared, visible, ultraviolet, x-rays, gamma rays
Consider an ideal solenoid of length L, N windings, and radius b (L is much longer than b). A current I is flowing through the wire windings. If the radius of the solenoid is doubled to 2b, but all the other quantities remain the same, the magnetic field inside the solenoid will
remain the same.
A capacitor C is connected in series with a resistor R across a battery and an open switch. If a second capacitor of capacitance 2C is connected in series with the first one, the time constant of the new RC circuit will be
smaller than before
Which one of the following is not an electromagnetic wave?
sound waves
A vertical wire carries a current vertically downward. To the east of this wire, the magnetic field points
south.
Two uncharged metal spheres, #1 and #2, are mounted on insulating support rods. A third metal sphere, carrying a positive charge, is then placed near #2. Now a copper wire is momentarily connected between #1 and #2 and then removed. Finally, sphere #3 is removed. In this final state
sphere #1 carries positive charge and #2 carries negative charge
A flat circular wire loop lies in a horizontal plane on a table and carries current in a counterclockwise direction when viewed from above. At this point, the earth's magnetic field points to the north and dips below the horizontal. Which side of the coil tends to lift off of the table due to the magnetic torque on the loop?
the south side
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in opposite directions
the wires push away from each other.
When different resistors are connected in parallel across an ideal battery, we can be certain that
their equivalent resistance is greater than the resistance of any one of the individual resistances.
A capacitor C is connected in series with a resistor R across a battery and an open switch. If a second capacitor of capacitance 2C is connected in parallel with the first one, the time constant of the new RC circuit will be
three times a large as before.
A long, straight, horizontal wire carries current toward the east. A proton moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the proton?
toward the north
At a particular instant, a proton moves toward the east in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it is
toward the north