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