Question 1

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 
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.

Accepted Answer

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Question 2

Equal currents of magnitude I travel out of the page in wires M and N.Eight directions are indicated by letters A through H. 
The direction of the magnetic field at point P is
A)E.
B)F.
C)G.
D)H.
E)A.

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Question 3

Two current loops are coaxial and coplanar.One has radius a and the other has radius 2a.Current 2I in the outer loop is antiparallel to current I in the inner loop.The magnitude of the magnetic field at the center of the two loops is
A)0.
B)  .
C)  .
D)  .
E)  .

Accepted Answer

By applying Biot-Savart's law, the magnetic field at the center of a current loop is given by B = μ0 I/2R, where μ0 is the magnetic constant, I is the current in the loop, and R is the radius of the loop. Since the two loops have opposite currents and are coaxial, the magnetic fields due to each loop cancel each other out at the center, resulting in a net magnetic field of 0.

Question 4

On the average,in a ferromagnetic domain permanent atomic magnetic moments are aligned ____ to one another.
A)antiparallel
B)parallel
C)perpendicular
D)alternately parallel and antiparallel
E)randomly relative

Accepted Answer

Ferromagnetic materials have permanent atomic magnetic moments that are aligned parallel to each other, which causes them to have a net magnetic moment.

Question 5

Two current loops are coaxial and coplanar.One has radius a and the other has radius 2a.Current 2I in the outer loop is parallel to current I in the inner loop.The magnitude of the magnetic field at the center of the two loops is
A)0.
B)  .
C)  .
D)  .
E)  .

Accepted Answer

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Question 6

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 
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.

Accepted Answer

According to the right-hand rule for magnetic forces, the force on the middle wire due to the top wire is directed downwards (out of the plane of the paper), and the force on the middle wire due to the bottom wire is directed upwards (into the plane of the paper). Since the two forces are in opposite directions, they cancel each other out in terms of the perpendicular components (i.e. out of/in to the plane of the wire). However, the parallel components (i.e. in the plane of the wire) add up, and therefore the net magnetic force on the middle wire is directed upwards (in the plane of the paper).

Question 7

Two parallel and coaxial current loops of radius a are placed a distance 2L apart.The current in each ring circulates in the same direction.At a point on the axis half way between the loops the magnetic field in T has magnitude
A)0.
B)  .
C)  .
D)  .
E)  .

Accepted Answer

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Question 8

When a ferromagnetic material that has been magnetized is brought to a temperature greater than the Curie temperature,what happens to its residual magnetism.
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.

Accepted Answer

When a ferromagnetic material is brought to a temperature greater than the Curie temperature, the thermal energy provided to the material causes the atoms to vibrate more vigorously, disrupting the alignment of the magnetic domains. As a result, the residual magnetism disappears, and the material becomes paramagnetic (weakly magnetic) or non-magnetic.

Question 9

Two parallel and coaxial current loops of radius a are placed a distance 2L apart.When you look along the axis at the loops,the current in one is clockwise,and counterclockwise in the other.At a point on the axis half way between the loops the magnetic field in T has magnitude
A)0.
B)  .
C)  .
D)  .
E)  .

Accepted Answer

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Question 10

Equal currents of magnitude I travel into the page in wires M and N.Eight directions are indicated by letters A through H. 
The direction of the magnetic field at point P is
A)B.
B)C.
C)D.
D)E.
E)F.

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Question 11

Equal currents of magnitude I travel out of the page in wire M and into the page in wire N.Eight directions are indicated by letters A through H. 
The direction of the magnetic field at point P is
A)A.
B)B.
C)C.
D)D.
E)E.

Accepted Answer

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Question 12

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
A)0.
B)  .
C)  .
D)  .
E)  .

Accepted Answer

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Question 13

An ideal solenoid of radius a has n turns per unit length and current I.The magnetic flux Φ_B through any area completely inside the solenoid,centered on the solenoid axis but at a 45° angle to the axis,so that it touches the inside of the solenoid,as shown below,is A) . B) . C)μ₀πa²nI. D)2μ₀πa²nI. E)0.

Accepted Answer

The magnetic field inside the solenoid is given by BS1U1B0=μnI. And, for a Gaussian surface lying completely inside the solenoid, the magnetic flux through that surface is given by ΦS1U1B1BS1U1B0=B0πa2cos(45°). Therefore, substituting the values, we get ΦS1U1B1BS1U1B0=μnIπa2cos(45°). Simplifying this expression gives us ΦS1U1B1BS1U1B0=μS1U1B10S1U1B0πaS1U1P12S1S1P0nI, which is equivalent to option C.

Question 14

Which of the following type(s)of materials is(are)repelled when a magnet is brought near by?
A)paramagnetic
B)diamagnetic
C)ferromagnetic
D)paramagnetic and ferromagnetic
E)paramagnetic,ferromagnetic,and diamagnetic

Accepted Answer

Diamagnetic materials have no unpaired electrons and are not attracted to magnets. Instead, they are repelled by the magnetic field. Both paramagnetic and ferromagnetic materials are attracted to magnets, so options A, C, and D are incorrect. Therefore, the correct answer is B, diamagnetic.

Question 15

An ideal solenoid of radius a has n turns per unit length and current I.The magnetic flux Φ_B through any circular area of radius a inside the solenoid,centered on and perpendicular to the solenoid axis is A) . B) . C)μ₀πa²nI. D)2μ₀πa²nI. E)0.

Accepted Answer

The magnetic field inside an ideal solenoid is constant and given by:

B = μnI

where μ is the permeability of free space, n is the number of turns per unit length, and I is the current.

The magnetic flux through a circular area of radius a inside the solenoid, centered on and perpendicular to the solenoid axis, is given by:

Φ = Bπa^2

Substituting the expression for B, we get:

Φ = (μnI)πa^2

Simplifying the expression, we get:

Φ = μnIπa^2

Therefore, the correct answer is (C).

Question 16

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
A)0.
B)  .
C)  .
D)  .
E)  .

Accepted Answer

According to the equation for the magnetic field generated by a long straight wire, the magnitude of the magnetic field depends on the distance from the wire. However, if the observer is traveling at the same velocity as the electrons in the wire parallel to the wire, the observer will not observe any magnetic field. This is due to the fact that the magnetic field is a result of the relative motion between the electrons in the wire and an observer outside the wire. Since the observer is moving at the same velocity as the electrons, there is no relative motion, and thus no magnetic field is observed. Therefore, the correct answer is A: 0.

Question 17

The magnetic moment of an electron (charge = −e;mass = m_e)moving in a circular orbit of radius r with speed v about a nucleus of mass m_N is proportional to A)r. B)v. C)vr. D)evr. E)m_Nvr.

Accepted Answer

The magnetic moment of a charged particle in circular motion is given by μ = evr/2, where e is the charge, v is the speed, and r is the radius of the orbit. Since the question asks for what the magnetic moment is proportional to, we can see that it is only proportional to evr, so the answer is (D). The other choices, (A), (B), (C), and (E), all have incorrect dependencies on the variables.

Question 18

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 
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.

Accepted Answer

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Question 19

Equal currents of magnitude I travel into the page in wire M and out of the page in wire N.Eight directions are indicated by letters A through H. 
The direction of the magnetic field at point P is
A)C.
B)E.
C)F.
D)G.
E)H.

Accepted Answer

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Question 20

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
A)  .
B) 
C)  .
D)  .
E)  .

Accepted Answer

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Quiz 30: Sources of the Magnetic Field

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

Equal currents of magnitude I travel out of the page in wires M and N.Eight directions are indicated by letters A through H. The direction of the magnetic field at point P is

Two current loops are coaxial and coplanar.One has radius a and the other has radius 2a.Current 2I in the outer loop is antiparallel to current I in the inner loop.The magnitude of the magnetic field at the center of the two loops is

On the average,in a ferromagnetic domain permanent atomic magnetic moments are aligned ____ to one another.

Two current loops are coaxial and coplanar.One has radius a and the other has radius 2a.Current 2I in the outer loop is parallel to current I in the inner loop.The magnitude of the magnetic field at the center of the two loops is

Two parallel and coaxial current loops of radius a are placed a distance 2L apart.The current in each ring circulates in the same direction.At a point on the axis half way between the loops the magnetic field in T has magnitude

When a ferromagnetic material that has been magnetized is brought to a temperature greater than the Curie temperature,what happens to its residual magnetism.

Two parallel and coaxial current loops of radius a are placed a distance 2L apart.When you look along the axis at the loops,the current in one is clockwise,and counterclockwise in the other.At a point on the axis half way between the loops the magnetic field in T has magnitude

Equal currents of magnitude I travel into the page in wires M and N.Eight directions are indicated by letters A through H. The direction of the magnetic field at point P is

Equal currents of magnitude I travel out of the page in wire M and into the page in wire N.Eight directions are indicated by letters A through H. The direction of the magnetic field at point P is

An ideal solenoid of radius a has n turns per unit length and current I.The magnetic flux Φ_B through any area completely inside the solenoid,centered on the solenoid axis but at a 45° angle to the axis,so that it touches the inside of the solenoid,as shown below,is

Which of the following type(s) of materials is(are) repelled when a magnet is brought near by?

An ideal solenoid of radius a has n turns per unit length and current I.The magnetic flux Φ_B through any circular area of radius a inside the solenoid,centered on and perpendicular to the solenoid axis is

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

The magnetic moment of an electron (charge = −e;mass = m_e) moving in a circular orbit of radius r with speed v about a nucleus of mass m_N is proportional to

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

Equal currents of magnitude I travel into the page in wire M and out of the page in wire N.Eight directions are indicated by letters A through H. The direction of the magnetic field at point P is