CHAPTER 21 - PHYSICS - MAGNETISM
true
A DC motor uses a split-ring commutator to change the direction of current flow. true false
false
A charge at rest in a magnetic field will be accelerated perpendicularly to the field lines. true false
parallel
A charge moving _______ to magnetic field lines does not experience any force from the magnetic field. parallel perpendicular
true
A charge moving parallel to magnetic field lines does not experience any force from the magnetic field. true false
true
A current loop will rotate until the magnetic field and the plane of the loop are perpendicular. true false
true
A galvanometer works by balancing an electromagnetic torque against a spring torque. true false
is a vector quantity.
A magnetic dipole moment has no directional character. is directed perpendicular to the plane of the current loop. has the same magnitude as the magnetic permeability. is a vector quantity.
true
A magnetic field can change the direction of a charged particle's motion without doing any work on the particle. true false
false
A magnetic field is not affected in any way by the material in which it is located. true false
false
A magnetic field surrounds stationary charged objects. true false
false
A moving electric charge is deflected in the direction of a magnetic field line. true false
the aurora.
A strong solar wind creates sun spots. the Van Allen belts. the magnetosphere. the aurora.
true
A wire carrying a current moving parallel to the orientation of the surrounding magnetic field will experience no magnetic force. true false
the unbalanced motion of electrical charges.
All magnetic fields ultimately have their source in paramagnetic particles. ferromagnetic particles. the unbalanced motion of electrical charges. magnetic domains.
true
All magnets have both north and south pole. true false
false
All materials have essentially the same response to an imposed magnetic field. true false
false
Aluminum is an example of a ferromagnetic material. true false
90°
At what angle between the magnetic field and the velocity vector of a moving charged particle is the magnetic force on the particle greatest? 30° 45° 90° 180°
true
Charged objects must be in motion to produce a magnetic field. true false
true
Coils of wire behave like stacks of current loops. true false
false
Coils of wire differ greatly from current loops. true false
true
For a rotating current loop, the magnitude of the torque is calculated using the equation = 2rF. true false
true
Forces on a current loop produce a torque that tends to rotate the loop. true false
true
If a velocity selector is used, particles with a speed of E/B will pass through the velocity selector undeflected. true false
false
In a simple DC motor, the stator contains the electric current that drives the motor, and the rotor contains the magnetic field. true false
false
In magnetic induction, a north pole induces an adjacent north pole in a susceptible material. true false
true
In magnetic induction, a north pole induces an adjacent south pole in a susceptible material. true false
false
It is never possible for a moving charge to pass through a magnetic field undeflected. true false
true
J. J. Thomson proved that cathode rays were negatively charged particles, which he called corpuscles. true false
false
James Clerk Maxwell was the first person to do experiments with magnets. true false
true
Like electric and gravitational fields, magnetic fields are three-dimensional. true false
are closer together near the magnetic poles.
Lines of magnetic force are closer together near the magnetic poles. will not readily pass through a sheet of paper. lengthen their paths based on the intensity of the magnetic field. follow straight-line paths.
false
Magnetic destination over the surface of the earth is relatively constant from one decade to the next. true false
false
Magnetic fields are two-dimensional representations of a magnet's effect on its surroundings. true false
true
Magnetic force is a conservative force. true false
true
Magnetic poles come in north-south pairs. true false
true
Materials differ in their responses to magnetic fields. true false
paramagnetic
Materials that are not very attracted to magnets are called ferromagnetic. diamagnetic. paramagnetic. ferrimagnetic.
diamagnetic
Materials that diminish a magnetic field are called ferromagnetic. diamagnetic. paramagnetic. none of the above.
true
Moving electrons create a magnetic field. true false
false
One tesla is approximately the strength of the terrestial magnetic field at the earth's surface. true false
true
Only those particles with a speed of E/B will pass through a velocity selector undeflected. true false
false
Permanent magnets must be surrounded by a current-carrying solenoid coil in order to produce a magnetic field. true false
true
Permanent magnets produce a magnetic field by themselves. true false
true
Petrus Peregrinus de Maricourt was the first person to do experiments with magnets. true false
tesla
The SI unit of magnetic field strength is the weber. oersted. henry. tesla.
true
The angular difference between the geographic north pole and the earth's magnetic north pole is called magnetic declination. true false
true
The closer the crossing angle between a charge's velocity and a magnetic field line is to 90 degrees, the greater the magnetic force on the charge. true fale
perpendicular
The direction of the force of a magnetic field on a moving charge is _____ to the direction of the field. parallel perpendicular
the magnetosphere.
The earth's effective magnetic field is contained within a region of space called the atmosphere. the magnetosphere. Van Allen belts. the aurora.
true
The earth's magnetic field is distorted by the solar wind. true false
false
The earth's magnetic field is symmetrical and uniform. true false
true
The earth's magnetic north pole is not aligned with its geographical north pole. true false
true
The effect of a magnet on its surroundings is best described by a magnetic field model. true false
false
The force of a magnetic field on a moving charge is in the direction of the charge's motion. true false
true
The force on a rotating coil is determined using the following equation: Fmag = nILB sin θ. true false
false
The force on a rotating coil is determined using the following equation: Fmag = nLB sin θ. true false
true
The formula for magnetic force in a coil of wire assumes that all the coils have the same dimensions. true false
true
The law of magnetic poles is similar to the law of charges. true false
false
The locations of the magnetic poles are constant. true false
true
The locations of the magnetic poles continuously change. true false
true
The magnetic declination charges over time as the magnetic poles move. true false
false
The magnetic declination for a given location on the earth's surface is constant over time. true false
both poles
The magnetic field of a magnet is strongest at the north pole. the south pole. both poles. between the poles.
true
The magnetic force on the charge has no component in the direction of the charge's motion. true false
true
The magnetic north pole of the earth is actually the south pole of the earth's magnetic field. true false
true
The magnitude of the force on a point charge is proportional to the speed of the charge and is a function of the angle at which the charge crosses the field lines. true false
nasa problems
The magnitude of the magnetic force on a point charge is calculated by the formula
true
The only way charges can produce a magnetic field is if they are moving. true false
true
The purpose of a DC motor is to convert electrical energy to mechanical work. true false
true
The purpose of a commutator is to reverse the current in the motor coil so that it can continue to turn in one direction. true false
relative permeability
The ratio of the strength of a magnetic field within a material to the strength of the same field in a vacuum is equivalent to _____. magnetic permeability relative permeability permeability of free space none of the above
true
The right hand rule for magnetic force is valid only for positive charges. true false
true
The solar wind distorts the shape of the magnetosphere. true false
true
The strength of a magnet depends not only on the dipole moments of its atoms but also on their orientation. true false
teslas
The strength of a magnetic field is measured in amperes. coulombs. teslas. webers.
false
The torque vector on a current loop in a magnetic field points in the direction of rotation. true false
false
Thomson used an anode-ray tube to show that anode rays were actually negatively charged particles of matter. true false
true
Thomson's experiment used cathode-ray tubes to show that cathode rays were actually negatively charged particles of matter. true false
true
When J. J. Thomson discovered negatively charged particles, he called them corpuscles. true false
false
When J. J. Thomson discovered negatively charged particles, he called them electrons. true false
nasa problems
Which of the following formulas is used to find the force of the magnetic field on a current loop?
Its magnitude is related to the strength of the magnetic field.
Which of the following is true of a magnetic dipole moment? It represents the electric effect of an atomic current. It is a scalar value. Its direction is opposite that of the atom's magnetic field. Its magnitude is related to the strength of the magnetic field. It is caused by the magnitude of paired electrons.
It describes the way a material affects a magnetic field inside it.
Which of the following statements about magnetic permeability is true? It describes the way a material affects a magnetic field inside it. It is the same for all materials. It does not depend on temperature. It does not depend upon the presence of a magnetic field.
It opposes an external field, tending to weaken the field or repel it.
Which of the following statements best describes diamagnetism? It is a magnetic property characteristic of inorganic materials. In the presence of an external magnetic field, it reinforces the imposed field. It opposes an external field, tending to weaken the field or repel it. It is a property of certain ferromagnetic material
the component of the current parallel to the field
Which of the following would not affect the magnetic force acting on a current-carrying wire? the length of the wire the component of the current parallel to the field the smallest angle between the current direction and the magnetic field vector the magnitude of current in the wire
Patrus Peregrinus de Maricourt
Who discovered that lodestones have poles? Hans Christian Oersted Nikola Tesla Patrus Peregrinus de Maricourt André Marie Ampère
