Question 1

A paramagnetic substance, in an external magnetic field, is thermally isolated. The field is then removed. As a result:

Accepted Answer

A)  the magnetic energy of the magnetic dipoles decreases 
B)  the temperature of the substance increases 
C)  the magnetization decreases, but only slightly 
D)  the magnetization reverses direction 
E)  none of the above

Question 2

Magnetic dipole X is fixed and dipole Y free to move. Dipole Y will initially:

Accepted Answer

A)  move toward X but not rotate 
B)  move away from X but not rotate 
C)  move toward X and rotate 
D)  move away from X and rotate 
E)  rotate but not translate

Question 3

Gauss' law for magnetism:

Accepted Answer

A)  can be used to find  due to given currents provided there is enough symmetry 
B)  is false because there are no magnetic poles 
C)  can be used with open surfaces because there are no magnetic poles 
D)  contradicts Faraday's law because one says $\phi$B = 0 and the other says $\varepsilon$ = -d$\phi$B/dt 
E)  none of the above

Question 4

A current of 1 A is used to charge a parallel plate capacitor with square plates. If the area of each plate is 0.6 m2 the displacement current through a 0.3 m2 area wholly between the capacitor plates and parallel to them is:

Accepted Answer

A)  1 A 
B)  2 A 
C)  0.7 A 
D)  0.5 A 
E)  0.25 A

Question 5

The behavior of ferromagnetic domains in an applied magnetic field gives rise to:

Accepted Answer

A)  hysteresis 
B)  ferromagnetism 
C)  the Curie law 
D)  a lowering of the Curie temperature 
E)  Gauss' law for magnetism

Question 6

A 1-A current is used to charge a parallel plate capacitor. A large square piece of paper is placed between the plates and parallel to them so it sticks out on all sides. The value of the integral  around the perimeter of the paper is:

Accepted Answer

A)  2 T .m 
B)  4 $\pi$*10-7 T. m 
C)  8.85 *10-12 T . m 
D)  10-7 T. m 
E)  not determined from the given quantities

Question 7

If an electron has an orbital angular momentum with magnitude L the magnitude of the orbital contribution to its magnetic dipole moment is given by:

Accepted Answer

A)  eL/m 
B)  eL/2m 
C)  2eL/m 
D)  mL/e 
E)  mL/2

Question 8

The diagram shows two small paramagnetic shperes, one near each end of a bar magnet. Which of the following statements is true?

Accepted Answer

A)  The force on 1 is toward the magnet and the force on 2 is away from the magnet 
B)  The force on 1 is away from the magnet and the force on 2 is away from the magnet 
C)  The forces on 1 and 2 are both toward the magnet 
D)  The forces on 1 and 2 are both away from the magnet 
E)  The magnet does not exert a force on either sphere

Question 9

Which of the following equations, along with a symmetry argument, can be used to calculate the magnetic field between the plates of a charging parallel plate capacitor with circular plates?

Accepted Answer

A)   
B)   
C)   
D)   
E)  none of these

Question 10

Paramagnetism is closely associated with:

Accepted Answer

A)  the tendency of electron dipole moments to align with an applied magnetic field 
B)  the tendency of electron dipole moments to align opposite to an applied magnetic field 
C)  the exchange force between electrons 
D)  the force exerted by electron dipole moments on each other 
E)  the torque exerted by electron dipole moments on each other

Question 11

A magnetic field parallel to the x axis with a magnitude that decreases with increasing x but does not change with y and z is impossible according to:

Accepted Answer

A)  Faraday's law 
B)  Ampere's law 
C)  Gauss' law for electricity 
D)  Gauss' law for magnetism 
E)  Newton's second law

Question 12

The polarity of an unmarked magnet can be determined using:

Accepted Answer

A)  a charged glass rod 
B)  a compass 
C)  an electroscope 
D)  another unmarked magnet 
E)  iron filings

Question 13

Four closed surfaces are shown. The areas Atop and Abot of the top and bottom faces and the magnitudes Btop and Bbot of the uniform magnetic fields through the top and bottom faces are given. The fields are perpendicular to the faces and are either inward or outward. Rank the surfaces according to the magnitude of the magnetic flux through the curved sides, least to greatest.

Accepted Answer

A)  1, 2, 3, 4 
B)  3, 4, 1, 2 
C)  1, 2, 4, 3 
D)  4, 3, 2, 1 
E)  2, 1, 4, 3

Question 14

Ferromagnetism is closely associated with:

Accepted Answer

A)  the tendency of electron dipole moments to align with an applied magnetic field 
B)  the tendency of electron dipole moments to align opposite to an applied magnetic field 
C)  the tendency of electron dipole moments to change magnitude in an applied magnetic field 
D)  the tendency of electron dipole moments to align with each other 
E)  the force exerted by electron dipole moments on each other

Question 15

A magnetic field  is applied to a diamagnetic substance. In the interior the magnetic field produced by the magnetic dipoles of the substance is:

Accepted Answer

A)  greater than  and in the opposite direction 
B)  less than  and in the opposite direction 
C)  greater than  and in the same direction 
D)  less than  and in the same direction 
E)  the same as

Question 16

The diagram shows two small diamagnetic spheres, one near each end of a bar magnet. Which of the following statements is true?

Accepted Answer

A)  The force on 1 is toward the magnet and the force on 2 is away from the magnet 
B)  The force on 1 is away from the magnet and the force on 2 is away from the magnet 
C)  The forces on 1 and 2 are both toward the magnet 
D)  The forces on 1 and 2 are both away from the magnet 
E)  The magnet does not exert a force on either sphere

Question 17

According to Gauss' law for magnetism, magnetic field lines:

Accepted Answer

A)  form closed loops 
B)  start at south poles and end at north poles 
C)  start at north poles and end at south poles 
D)  start at both north and south poles and end at infinity 
E)  do not exist

Question 18

Consider the four Maxwell equations:  Which of these must be modified if magnetic poles are discovered?

Accepted Answer

A)  only I 
B)  only II 
C)  only II and III 
D)  only III and IV 
E)  only II, III, IV

Question 19

A cylindrical region contains a uniform electric field that is parallel to the axis and is changing with time. If r is the distance from the cylinder axis the magnitude of the magnetic field outside the region is:

Accepted Answer

A)  0 
B)  proportional to 1/r 
C)  proportional to r2 
D)  proportional to 1/r2 
E)  proportional to r

Question 20

The diagram shows one plate of a parallel-plate capacitor from within the capacitor. The plate is circular and has radius R. The dashed circles are four integration paths have radii of r1 = R/4, r2 = R/2, r3 =3 R/2, and r4 = 2R. Rank the paths according to the magnitude of  around the paths during the discharging of the capacitor, least to greatest.

Accepted Answer

A)  1, 2 and 3 tie, then 4 
B)  1, 2, 3, 4 
C)  1, then 2 and 4 tie, then 3 
D)  4, 3, 1, 2 
E)  all tie

Exam 32: Maxwells Equations; Magnetism of Matter