Chapter 19 Conceptual Questions
The magnetic forces that two parallel wires with unequal currents flowing in opposite directions exert on each are _______. Select one: a. attractive and equal in magnitude. b. in the same direction and equal in magnitude. c. in the same direction and unequal in magnitude d. repulsive and unequal in magnitude. e. attractive an unequal in magnitude. f. repulsive and equal in magnitude. g. zero
f. repulsive and equal in magnitude.
It is NOT possible for an iron magnet to lose its magnetic properties. Select one: True False
False
A current carrying loop can be positioned in a magnetic field such that the net torque is equal to zero. Select one: True False
True
The magnetic field surrounding a solenoid resembles that of a bar magnet. Select one: True False
True
When you cut a magnet in half you end up with two smaller magnets rather than a magnetic monopole. Select one: True False
True
When the number of turns in a solenoid and its length are both doubled, the ratio of the magnitude of the new magnetic field inside to the magnitude of the original magnetic field inside is: Select one: a. 0.25 b. 0.50 c. 1 d. 2 e. 4
c. 1
If you were to travel parallel to an infinitely long straight wire with current I at the same velocity as the electrons in the wire at a distance a from the wire, the magnitude of the magnetic field (according to your measuring instruments) would be Select one: a. 0. b. μ0I/2πa. c. μ0I/πa. d. 2μ0I/πa. e. 4μ0I/πa.
a. 0.
We find that 2N current loops are coplanar and coaxial. The first has radius a and current I. The second has radius 2a and current 2I, and the pattern is repeated up to the Nth, which has radius Na and current NI. The current in the loops alternates in direction from loop to loop as seen from above. Thus the current in the first loop is counterclockwise, in the next clockwise, up to the last loop where it is again clockwise. The magnitude of the magnetic field at the center of the loops is Select one: a. 0. b. μ0I/2Na. c. μ0I/Na. d. μ0NI/2a. e. μ0NI/a.
a. 0.
Two long parallel wires lie in the xz plane. One wire passes through the point (-2 m, 0, 0) and the other through the point (+2 m, 0, 0). The wires carry equal currents in the positive z direction. 1. The magnetic field at (-3 m, 0, 0) is in the negative y direction. 2. The magnetic field at (-1 m, 0, 0) is in the positive y direction. 3. The magnetic field at (+1 m, 0, 0) is in the positive y direction. 4. The magnetic field at (+3 m, 0, 0) is in the negative y direction. Select one: a. 1 and 2 are correct. b. 1 and 4 are correct. c. 2 and 3 are correct. d. 3 and 4 are correct. e. None of the above are correct.
a. 1 and 2 are correct.
A current element (length = 1.0 cm) lies along the x axis with its center at x = 0 and carries a 20-A current in the positive x direction. Consider only the field of this current element and decide which combination of the following statements is correct. 1. The field at (0, 0, 1.0 m) is in the positive z direction. 2. The field at (0, 1.0 m, 0) is in the negative y direction. 3. The field at (1.0 m, 0, 0) is zero. 4. The field at (0, 0, 1.0 m) is in the negative y direction. Select one: a. 3 and 4 b. 1 and 3 c. 2 and 4 d. 1 and 2 e. None of these
a. 3 and 4
Consider two current-carrying circular loops. Both are made from one strand of wire and both carry the same current, but one has twice the radius of the other. Compared to the magnetic moment of the smaller loop, the magnetic moment of the larger loop is _______. Select one: a. 4 times stronger. b. 2 times stronger. c. 16 times stronger. d. 8 times stronger.
a. 4 times stronger.
A positively charged particle has a velocity in the negative z direction at point P. The magnetic force on the particle at this point is in the negative y direction. Which one of the following statements about the magnetic field at point P can be determined from this data? Select one: a. Bx is positive. b. Bz is positive. c. By is negative. d. By is positive. e. Bx is negative.
a. Bx is positive.
Which of the following describes the lines of magnetic field in the vicinity of a proton beam as they shoot across a laboratory? Select one: a. Concentric circles around the beam b. Parallel to the beam c. Radial and toward the beam d. Radial and away from the beam e. There is no magnetic field
a. Concentric circles around the beam
What direction do the magnetic field lines point? Select one: a. From the North to South magnetic poles. b. From the South to North magnetic poles. c. Magnetic field lines do not have a direction since they go between poles. d. Form circles that go around the magnet.
a. From the North to South magnetic poles.
From your perspective, the current in a ring is moving in a clockwise direction. In the center of the ring, what is the direction of the magnetic field? Select one: a. Into the ring. b. Is zero c. Out of the ring.
a. Into the ring.
A long, vertical, metallic wire carries downward electric current. What is the direction of the magnetic field it creates at a point 2 cm horizontally east of the center of the wire? Select one: a. South b. North c. East d. West e. up f. down
a. South
What configuration will give a magnetic dipole the most amount of energy within an electric field? Select one: a. The dipole and the field are pointed in opposite directions. b. The dipole and the field are pointed in the same direction. c. The dipole and the field are at at 45 degree angle. d. The energy does not depend on the configuration.
a. The dipole and the field are pointed in opposite directions.
Different units can be used to measure the same physical quantity, differing only by some multiplicative factor. The cgs unit for magnetic field, the gauss, is equal to ________ tesla. Select one: a. 104 b. 10-4 c. 0.5 d. These units do not measure the same physical quantity.
b. 10-4
The north end of a bar magnet is used to pick up a nail. The nail is then removed and the south end of the magnet is placed close to the nail. The nail itself in not magnetic. What will the nail do? Select one: a. The nail will also be attracted to the other pole. b. The nail will move away from the magnet. c. Nothing will happen.
a. The nail will also be attracted to the other pole.
A loose spiral spring is hung form the ceiling and a large current is sent through it. The coils move ... Select one: a. closer together. b. farther apart. c. they do not move at all.
a. closer together.
Geophysicists today generally attribute the existence of the Earth's magnetic field to which of the following? Select one: a. convection currents within the liquid interior b. iron ore deposits in the crust c. nickel-iron deposits in the crust d. solar flares
a. convection currents within the liquid interior
Which of the following is not a hard magnetic material? Select one: a. iron b. cobalt c. nickel d. both b and c
a. iron
An electron moving in the positive x direction experiences a magnetic force in the positive z direction. If Bx = 0, what is the direction of the magnetic field? Select one: a. negative y direction b. positive y direction c. negative z direction d. positive z direction e. negative x direction
a. negative y direction
When calculating the force of a magnetic field on a moving charge, we use a cross product. If the magnetic field is perpendicular to the charge's velocity vector, the direction of the force will be _______. Select one: a. perpendicular to both the magnetic field and the velocity vector. b. in the plane formed by the direction of the magnetic field and the velocity vector. c. in the same direction as the magnetic field. d. in the same direction as the velocity vector.
a. perpendicular to both the magnetic field and the velocity vector.
A wire carries current in the plane of this screen toward the top of the page. The wire experiences a magnetic force toward the right edge of the screen. The direction of the magnetic field causing this force is _____ . Select one: a. pointed upward out of the screen. b. in the plane of the screen and pointed toward the left edge. c. in the plane of the screen and pointed toward the bottom edge. d. pointed downward into the screen.
a. pointed upward out of the screen.
A charged particle is moving perpendicular to a magnetic field in a circle with radius r. The magnitude of the magnetic field is increased. Compared to the initial radius of circular path, the radius of the new path is... Select one: a. smaller. b. larger. c. equal in size.
a. smaller.
The path of a charged particle moving parallel to a uniform magnetic field will be a: Select one: a. straight line. b. circle. c. ellipse. d. parabola.
a. straight line.
The reason the north pole of a bar magnet free to rotate points north is because Select one: a. the south geographic pole of the earth is the earth's magnetic north pole. b. the south geographic pole of the earth is the earth's magnetic south pole. c. there is a net accumulation of negative magnetic charge at the earth's south geographic pole. d. there is a net accumulation of positive magnetic charge at the earth's north geographic pole. e. the north geographic pole of the earth is the earth's magnetic north pole.
a. the south geographic pole of the earth is the earth's magnetic north pole.
A square coil and an equliladral triangular coil each have sides of length L. The triangular coil has twice as many turns as the square coil. If a the same current is sent through each coil, when the coils are placed in the same uniform magnetic field making an angle of 30° with the planes of the coils, which coil experiences the greater torque? Select one: a. the square coil b. the triangular coil c. Both coils experience the same torque. d. It depends on the magnitude of the magnetic field that the coils are placed in.
a. the square coil
A hollow copper tube carries a current along its length. What is the value of B within the tube. Select one: a. zero. b. μI. c. μI/2r d. μIL
a. zero.
An experiment is conducted on a long straight wire of diameter d. A constant current is sent through the wire and the magnetic field on the surface of the wire is measured to be B. The experiment is then repeated with the same current but with a wire diameter of 2d. The magnetic field measured on the surface of this second wire will be ... Select one: a. B/4 b. B/2 c. B d. 2B e. 4B
b. B/2
A soft magnetic material has which property? Select one: a. It cannot be magnetized. b. It is easy to magnetize. c. It is hard to magnetize. d. It attracts slowly moving charges.
b. It is easy to magnetize.
Bert says that a charged particle in a vacuum can travel in a helix only if a uniform electric field and a uniform magnetic field are both present and both parallel to the axis of the helix. Stuart says that only a magnetic field with a component parallel to the axis of the helix is needed. Which one, if either, is correct, and why? Select one: a. Bert, because the charged particle's velocity can have a vertical component only if an electric field in the vertical direction is present. b. Stuart, because a component of velocity in the vertical direction is not changed by a vertical component of a magnetic field. c. Bert, because a component of velocity in the vertical direction is changed by a vertical component of a magnetic field. d. Stuart, because an electric field in the vertical direction would cause the particle to come to a complete stop. e. Neither, because particles cannot move in helical paths in the presence of magnetic and electric fields.
b. Stuart, because a component of velocity in the vertical direction is not changed by a vertical component of a magnetic field.
The following statements all refer to the human brain when mental activity is occurring. Which statement is correct? Select one: a. In order to detect electric currents in the brain, you must open the skull and make direct electrical contact with the brain. b. The electric currents in the brain can be detected outside the brain by detecting the magnetic fields they produce. c. The electric currents in the brain can be mapped by shaving a person's head and dropping iron filings on the head. d. The electric currents in the brain produce an aura that can be detected visually. e. The electric currents in the brain cannot be detected by any means.
b. The electric currents in the brain can be detected outside the brain by detecting the magnetic fields they produce.
When a ferromagnetic material that has been magnetized is brought to a temperature greater than the Curie temperature, what happens to its residual magnetism. Select one: a. Nothing happens to the residual magnetism. b. The residual magnetism disappears. c. The residual magnetism reaches it's highest value. d. All the magnetic domains causing magnetism become a single domain. e. The material of the magnet melts causing currents that are magnetic.
b. The residual magnetism disappears.
A proton moving with a speed of 3.0 ´ 10^5 m/s perpendicular to a uniform magnetic field of 0.20 T will follow which of the paths described below? (qp = 1.6 ´ 10^-19 C and mp = 1.67 ´ 10^-27 kg) Select one: a. a straight line path b. a circular path of 1.6 cm radius c. a circular path of 3.1 cm radius d. a circular path of 0.78 cm radius
b. a circular path of 1.6 cm radius
The magnetic pole of the Earth nearest the geographic North Pole corresponds to which of the following? Select one: a. a magnetic north pole b. a magnetic south pole c. a magnetic arctic pole d. a magnetic Antarctic pole
b. a magnetic south pole
The magnetic field of the Earth is believed responsible for which of the following? Select one: a. deflection of both charged and uncharged cosmic rays b. deflection of charged cosmic rays c. ozone in the upper atmosphere d. solar flares
b. deflection of charged cosmic rays
Which of the following type(s) of materials is(are) repelled when a magnet is brought near by? Select one: a. paramagnetic b. diamagnetic c. ferromagnetic d. paramagnetic and ferromagnetic e. paramagnetic, ferromagnetic, and diamagnetic
b. diamagnetic
The current in a long wire creates a magnetic field in the region around the wire. How is the strength of the field at distance r from the wire center related to the magnitude of the field? Select one: a. field directly proportional to r b. field inversely proportional to r c. field directly proportional to r2 d. field inversely proportional to r2
b. field inversely proportional to r
A proton is released such that its initial velocity is from right to left across this page. The proton's path, however, is deflected in a direction toward the bottom edge of the page due to the presence of a uniform magnetic field. What is the direction of this field? Select one: a. out of the page b. into the page c. from bottom edge to top edge of the page d. from right to left across the page
b. into the page
When a magnetic field causes a charged particle to move in a circular path, the only quantity listed below which the magnetic force changes significantly as the particle goes around in a circle is the particle's: Select one: a. energy. b. momentum. c. radius for the circle. d. time to go around the circle once.
b. momentum.
A proton moves across the Earth's equator in a northeasterly direction. At this point the Earth's magnetic field has a direction due north and is parallel to the surface. What is the direction of the force acting on the proton at this instant? Select one: a. toward the northwest b. out of the Earth's surface c. into the Earth's surface d. toward the northeast
b. out of the Earth's surface
A long wire lies in a tangle on the surface of a table, as shown below. When a current is run through the wire as shown, the largest component of the magnetic field at X points Select one: a. into the table. b. out of the table. c. parallel to the nearest segment of wire. d. antiparallel to the nearest segment of wire. e. along a circle which has its center at the center of the overall loop.
b. out of the table.
On the average, in a ferromagnetic domain permanent atomic magnetic moments are aligned ____ to one another. Select one: a. antiparallel b. parallel c. perpendicular d. alternately parallel and antiparallel e. randomly relative
b. parallel
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 toward you, and the wire on your left carries current away from you. From you point of view, the magnetic field at the point exactly midway between the two wires.... Select one: a. points up. b. points down. c. points toward you. d. is zero.
b. points down.
Which of the following locations has the smallest (in magnitude) magnetic declination? Select one: a. Washington state b. the South Carolina - Georgia border c. the San Francisco - Oakland area d. western Colorado
b. the South Carolina - Georgia border
A current in a solenoid coil creates a magnetic field inside that coil. The field strength is directly proportional to: Select one: a. the coil area. b. the current. c. Both A and B are valid choices. d. None of the above choices are valid.
b. the current.
A straight wire of length ℓ is oriented east-west and is in a magnetic field B pointing north. The wire is moving downward at a constant speed v. Which end of the wire is positively charged? Select one: a. neither b. the east end c. the west end d. both ends
b. the east end
An explorer walks into a lab in a science building. She has a compass in her hand and finds that the south pole of her compass points toward the room's East wall when she is nearer that wall and toward the west wall when she is nearer that wall. You could explain this if magnetized metal had been installed in the East and West walls with North poles pointing into the room. If no magnetic material was installed in the North or South walls of the room, she would expect that Select one: a. the south pole of the compass would tend to point toward those walls. b. the north pole of the compass would tend to point toward those walls. c. the compass needle would not point in any particular direction. d. the north pole of the compass needle would tend to point toward the centers of those walls, but the south pole would tend to point toward the sides of those walls. e. the south pole of the compass needle would tend to point toward the centers of those walls, but the north pole would tend to point toward the sides of those walls.
b. the north pole of the compass would tend to point toward those walls.
When a microwave filter consisting of vertical parallel metal rods is in the absorbing position, oscillating currents are set up in the rods. At any one instant, the current in each rod has the same magnitude and direction. At that instant Select one: a. the rods will try to move apart horizontally. b. the rods will try to move together horizontally. c. the rods will try to shift vertically upwards. d. the rods will try to shift vertically downwards. e. the rods will not be affected because the source of current is not a battery.
b. the rods will try to move together horizontally.
Consider two long, straight parallel wires, each carrying a current I. If the currents are flowing in opposite directions: Select one: a. the two wires will attract each other. b. the two wires will repel each other. c. the two wires will exert a torque on each other. d. neither wire will exert a force on the other.
b. the two wires will repel each other.
Assume that a uniform magnetic field is directed into this page. If an electron is released with an initial velocity directed from the bottom edge to the top edge of the page, which of the following describes the direction of the resultant force acting on the electron? Select one: a. out of the page b. to the right c. to the left d. into the page
b. to the right
A horizontal wire of length 3.0 m carries a current of 6.0 A and is oriented so that the current direction is 50° S of W. The Earth's magnetic field is due north at this point and has a strength of 0.14 ´ 10-4 T. What is the direction of the force on the wire? Select one: a. out of the Earth's surface b. toward the Earth's surface c. due east d. 40° S of E
b. toward the Earth's surface
Two solenoids are each made of 2 000 turns of copper wire per meter. Solenoid I is 2 m long, while solenoid II is 1 m long. When equal currents are present in the two solenoids, the ratio of the magnetic field BI along the axis of solenoid I to the magnetic field BII along the axis of solenoid II, BI/BII, is Select one: a. 1/4. b. 1/2. c. 1. d. 2. e. 4.
c. 1.
The force on a charged particle created by its motion in a magnetic field is maximum at what angle between the particle velocity and field? Select one: a. zero b. 180° c. 90° d. 45°
c. 90°
A current in a solenoid with N turns creates a magnetic field at the center of that loop. The field strength is directly proportional to: Select one: a. number of turns in the loop. b. current strength. c. Both choices A and B are valid. d. None of the above are valid.
c. Both choices A and B are valid.
The direction of the force on a current carrying wire located in an external magnetic field is which of the following? Select one: a. perpendicular to the current b. perpendicular to the field c. Both choices A and B are valid. d. None of the above are valid.
c. Both choices A and B are valid.
Solenoid #1 has a length L, cross-sectional area A, and N turns. Solenoid #2 has a length 2L, cross-sectional area 2A, and 2N turns. Which solenoid has the greater magnetic field at its center when equal currents are going through them? Select one: a. #1 b. #2 c. Both have the same magnetic field. d. Since it depends on the values of A and L, none of the above are correct.
c. Both have the same magnetic field.
Square coil A has 2N turns and sides of length L, and square coil B has N turns and sides of length 2L. When a current of 2 amps is sent through coil A and a current of 1 amp is sent through coil B, which coil has the greater magnetic moment? Select one: a. coil A b. coil B c. Both have the same magnetic moment. d. More information is needed.
c. Both have the same magnetic moment.
A proton with initial kinetic energy E is moving in circular motion in a uniform magnetic field. When it has completed one eighth of a revolution, what is its kinetic energy? Select one: a. 1.4 E b. 0.71 E c. E d. The value is not given.
c. E
Consider a solenoid that is very long compared with its radius. Of the following choices, what is the most effective way to increase the magnetic field in the interior of the solenoid? Select one: a. Double its length, keeping the number of turns per unit length constant. b. Reduce the radius by half, keeping the number of turns per unit length constant. c. Overwrap the entire solenoid with an additional layer of the current-carrying wire. d. Double the radius, keeping the number of turns per unit length constant.
c. Overwrap the entire solenoid with an additional layer of the current-carrying wire.
A charged particle (mass = M, charge = Q > 0) moves in a region of space where the magnetic field has a constant magnitude of B and a downward direction. What is the magnetic force on the particle at an instant when it is moving horizontally toward the north with speed V? Select one: a. QVB toward the east b. Zero c. QVB toward the west d. QVB upward e. QVB toward the south
c. QVB toward the west
Electrical charges and magnetic poles have many similarities, but one difference is: Select one: a. opposite magnetic poles repel. b. one magnetic pole cannot create magnetic poles in other materials. c. a magnetic pole cannot be isolated. d. magnetic poles do not produce magnetic fields.
c. a magnetic pole cannot be isolated.
The force exerted on a current-carrying wire located in an external magnetic field is directly proportional to which of the following? Select one: a. current strength b. field strength c. both the current and the field strength d. None of the above are valid.
c. both the current and the field strength
The dip angle is: Select one: a. another term for magnetic declination. b. a measure of the tendency for a compass to point south. c. close to or at zero near the equator. d. close to or at zero just north of Hudson Bay.
c. close to or at zero near the equator.
The magnetic field in a region of space is parallel to the surface of a long flat table. Imagine that this page is lying flat on the table. When current is present in the coil, which is lying on the table, the coil tends to rotate so that the left side moves up and the right side moves down. The magnetic field is Select one: a. directed parallel to the page and downwards. b. directed parallel to the page and upwards. c. directed parallel to the page and to the right. d. directed parallel to the page and to the left. e. in a direction that cannot be determined in this experiment
c. directed parallel to the page and to the right.
A circular current loop is placed in an external magnetic field. How is the torque related to the radius of the loop? Select one: a. directly proportional to radius b. inversely proportional to radius c. directly proportional to radius squared d. inversely proportional to radius squared
c. directly proportional to radius squared
You stand near the earth's equator. A positively charged particle that starts moving parallel to the surface of the earth in a straight line directed east is initially deflected upwards. If you know there are no electric fields in the vicinity, a possible reason why the particle does not initially acquire a downward component of velocity is because near the equator the magnetic field lines of the earth are directed Select one: a. upward. b. downward. c. from south to north. d. from north to south. e. from east to west.
c. from south to north.
A charged particle enters a bubble chamber filled with liquid hydrogen with an initial kinetic energy, Ko. The particle travels in the horizontal plane in a magnetic field that is in the vertical direction. After a certain time, the particle's kinetic energy has been reduced by a factor of 2 due to collisions with hydrogen atoms. At this point, the radius of curvature of the particle's path ... Select one: a. has been reduced by a factor of 4. b. has been reduced by a factor of 2. c. has been reduced by a factor of √2. d. has increased by a factor of 4. e. has increased by a factor of 2. f. has increased by a factor of √2 g. is still the same as the original radius of curvature.
c. has been reduced by a factor of √2.
To increase the sensitivity of a galvanometer, you should.... Hint: To be more sensitive, do you want a larger or smaller deflection for a given current? Select one: a. increase the number of coil turns and increase the spring constant. b. decrease the number of coil turns and decrease the spring constant. c. increase the number of coil turns and decrease the spring constant. d. decrease the number of coil turns and increase the spring constant.
c. increase the number of coil turns and decrease the spring constant.
Three coplanar parallel straight wires carry equal currents I to the right as shown below. The current in the upper two wires is directed to the right, but the current in the bottom wire is directed to the left. Each pair of wires is a distance a apart. The direction of the magnetic force on the middle wire Select one: a. is up out of the plane of the wires. b. is down into the plane of the wires. c. is in the plane of the wires, directed upwards. d. is in the plane of the wires, directed downwards e. cannot be defined, because there is no magnetic force on the middle wire.
c. is in the plane of the wires, directed upwards.
In a mass spectrometer, an ion will have a smaller radius for its circular path if: Select one: a. its speed is greater. b. its mass is greater. c. its charge is greater. d. the magnetic field is weaker.
c. its charge is greater.
The magnetic force on a point charge in a magnetic field is largest, for a given speed, when it Select one: a. moves in the direction of the magnetic field. b. moves in the direction opposite to the magnetic field. c. moves perpendicular to the magnetic field. d. has velocity components both parallel to and perpendicular to the field.
c. moves perpendicular to the magnetic field.
The north-pole end of a bar magnet is held near a positively charged piece of plastic. The plastic is Select one: a. attracted. b. repelled. c. unaffected by the magnet.
c. unaffected by the magnet.
A wire carries current in the plane of this screen toward the top of the page. The wire experiences a magnetic force toward the right edge of the screen. The direction of the magnetic field causing this force is... Select one: a. in the plane of the screen and toward the left edge. b. in the plane of the screen and toward the bottom edge. c. upward out of the screen. d. downward into the screen.
c. upward out of the screen.
Three particles of equal charge, X, Y, and Z, enter a uniform magnetic field B. X has velocity of magnitude v parallel to the field. Y has velocity of magnitude v perpendicular to the field. Z has equal velocity components v parallel and perpendicular to the field. Rank the radii of their orbits from least to greatest. Select one: a. Rx = Ry < Rz. b. Rx < Ry < Rz. c. Rx = Ry = Rz. d. Rx > Ry > Rz. e. Rx < Ry = sqrt(2) x Rz
d. Rx > Ry > Rz.
Equal charges, one at rest, the other having a velocity of 10^4 m/s, are released in a uniform magnetic field. Which charge has the largest force exerted on it by the magnetic field? Select one: a. The charge that is at rest. b. The charge that is moving, if its velocity is parallel to the magnetic field direction when it is released. c. The charge that is moving if its velocity makes an angle of 45 degrees with the direction of the magnetic field when it is released. d. The charge that is moving if its velocity is perpendicular to the magnetic field direction when it is released. e. All the charges above experience equal forces when released in the same magnetic field.
d. The charge that is moving if its velocity is perpendicular to the magnetic field direction when it is released.
Two insulated current-carrying straight wires of equal length are arranged in the lab so that Wire A carries a current northward and Wire B carries a current eastward, the wires crossing at their midpoints separated only by their insulation. Which of the following statements are true? Select one: a. The net force on Wire B is southward. b. The net force on Wire A is westward. c. There are no forces in this situation. d. There are forces, but the net force on each wire is zero.
d. There are forces, but the net force on each wire is zero.
A stationary positive charge +Q is located in a magnetic field B, which is directed toward the right as indicated. The direction of the magnetic force on Q is: Select one: a. toward the right. b. up. c. down. d. There is no magnetic force.
d. There is no magnetic force.
The term magnetic declination refers to which of the following? Select one: a. angle between Earth's magnetic field and Earth's surface b. Earth's magnetic field strength at the equator c. tendency for Earth's field to reverse itself d. angle between directions to true north and magnetic north
d. angle between directions to true north and magnetic north
If a charged particle is moving in a uniform magnetic field, its path can be: Select one: a. a straight line. b. a circle. c. a helix. d. any of the above.
d. any of the above.
By using a compass to measure the magnetic field direction at various points adjacent to a long straight wire, you can show that the wire's magnetic field lines are Select one: a. straight lines in space that go from one magnetic charge to another. b. straight lines in space that are parallel to the wire. c. straight lines in space that are perpendicular to the wire. d. circles that have their centers on the wire and lie in planes perpendicular to the wire. e. circles that have the wire lying along a diameter of the circle.
d. circles that have their centers on the wire and lie in planes perpendicular to the wire.
The magnetic moment of an electron (charge = -e; mass = me) moving in a circular orbit of radius r with speed v about a nucleus of mass mN is proportional to Select one: a. r. b. v. c. vr. d. evr. e. mNvr.
d. evr.
A current in a long, straight wire produces a magnetic field. The magnetic field lines: Select one: a. go out from the wire to infinity. b. come in from infinity to the wire. c. form circles that pass through the wire. d. form circles that go around the wire.
d. form circles that go around the wire.
The right-hand rule allows one to find a property of the interaction of a magnetic field with a charged particle. The right-hand rule applied to moving charges: Select one: a. results in positive charges moving clockwise. b. results in negative charges moving clockwise. c. can be used for positive charges only. d. gives the direction of the force on a charge moving in a magnetic field.
d. gives the direction of the force on a charge moving in a magnetic field.
One reason why we know that magnetic fields are not the same as electric fields is because the force exerted on a charge +q Select one: a. is in opposite directions in electric and magnetic fields. b. is in the same direction in electric and magnetic fields. c. is parallel to a magnetic field and perpendicular to an electric field. d. is parallel to an electric field and perpendicular to a magnetic field. e. is zero in both if the charge is not moving.
d. is parallel to an electric field and perpendicular to a magnetic field.
There is a magnetic force on a particle. It is possible that the particle is: Select one: a. uncharged. b. stationary. c. moving in the direction of the magnetic field. d. not part of a wire.
d. not part of a wire.
We find that N current loops are coplanar and coaxial. The first has radius a and current I. The second has radius 2a and current 2I, and the pattern is repeated up to the Nth, which has radius Na and current NI. The current in each loop is counterclockwise as seen from above. The magnitude of the magnetic field at the center of the loops is Select one: a. μ0I/2Na. b. μ0I/Na. c. μ0I/2a. d. μ0NI/2a. e. μ0NI/a.
d. μ0NI/2a.
A solenoid consists of 100 circular turns of copper wire. Parts of three turns, A, B and C, are shown below. When a current flows through the coil, Select one: a. both A and C are repelled by B. b. A is attracted to B; C is repelled by B. c. neither A nor C is attracted to or repelled by B. d. A is repelled by B; C is attracted to B. e. both A and C are attracted to B.
e. both A and C are attracted to B.
Three coplanar parallel straight wires carry equal currents I as shown below. The current in the outer wires is directed to the right, and that in the middle wire is directed to the left. Each pair of wires is a distance a apart. The direction of the magnetic force on the middle wire Select one: a. is up out of the plane of the wires. b. is down into the plane of the wires. c. is in the plane of the wires, directed upwards. d. is in the plane of the wires, directed downwards e. cannot be defined, because there is no magnetic force on the middle wire.
e. cannot be defined, because there is no magnetic force on the middle wire.
Three coplanar parallel straight wires carry equal currents I to the right as shown below. Each pair of wires is a distance a apart. The direction of the magnetic force on the middle wire Select one: a. is up out of the plane of the wires. b. is down into the plane of the wires. c. is in the plane of the wires, directed upwards. d. is in the plane of the wires, directed downwards e. cannot be defined, because there is no magnetic force on the middle wire.
e. cannot be defined, because there is no magnetic force on the middle wire.
A positively charge particle is moving to the right side of the screen and the magnetic field is pointed to the top of the screen. What is the direction of the force of the magnetic field on the particle? Select one: a. toward the top of the screen. b. toward the bottom of the screen. c. toward the left edge of the screen. d. toward the right edge of the screen. e. out of the screen. f. into the screen.
e. out of the screen.
At a point in space where the magnetic field is measured, the magnetic field produced by a current element Select one: a. points radially away in the direction from the current element to the point in space. b. points radially in the direction from the point in space towards the current element. c. points in a direction parallel to the current element. d. points in a direction parallel to but opposite in direction to the current element. e. points in a direction that is perpendicular to the current element and perpendicular to the radial direction.
e. points in a direction that is perpendicular to the current element and perpendicular to the radial direction.
The magnitude of the torque on magnetic dipole does not depend on ... Select one: a. the magnitude of the electric field. b. the size of the loop. c. the amount of current traveling through the loop. d. the angle between the loop and the magnetic field. e. the type of charge carrier within the loop.
e. the type of charge carrier within the loop.
