Question 1

Ampère's law is valid

Accepted Answer

A) when there is a high degree of symmetry in the geometry of the situation. 
B) when there is no symmetry. 
C) when the current is constant. 
D) when the magnetic field is constant. 
E) for all of these conditions. 
A) when there is a high degree of symmetry in the geometry of the situation. 
B) when there is no symmetry. 
C) when the current is constant. 
D) when the magnetic field is constant. 
E) for all of these conditions.

Question 2

The electron orbiting a proton in a hydrogen atom has a speed of v = 2.19 $\times$ 106 m/s.The magnetic moment of the electron when it is orbiting at the Bohr's radius (= 0.529 nm)is

Accepted Answer

A) 9.27 $\times$ 10-24 A . m2 
B) 1.86 $\times$ 10-23 A . m2 
C) 3.71 $\times$ 10-23 A . m2 
D) 2.62 $\times$ 10-23 A . m2 
E) none of these is correct. 
A) 9.27 $\times$ 10-24 A . m2 
B) 1.86 $\times$ 10-23 A . m2 
C) 3.71 $\times$ 10-23 A . m2 
D) 2.62 $\times$ 10-23 A . m2 
E) none of these is correct.

Question 3

Nickel has a density of 8.70 g/cm3 and a molecular mass of 58.7 g/mol.Its magnetic moment is 0.587 Bohr magnetons (1 Bohr magneton = 9.27 $\times$ 10-24 A · m2).What is its saturation magnetization?

Accepted Answer

A) 4.85 $\times$ 109 A/m 
B) 8.92 $\times$ 105 A/m 
C) 9.27 $\times$ 10-24 A/m 
D) 8.92 $\times$ 1028 A/m 
E) 4.85 $\times$ 105 A/m 
A) 4.85 $\times$ 109 A/m 
B) 8.92 $\times$ 105 A/m 
C) 9.27 $\times$ 10-24 A/m 
D) 8.92 $\times$ 1028 A/m 
E) 4.85 $\times$ 105 A/m

Question 4

At a certain instant of time a particle with charge q = 25 $\mu$C is located at x = 4.0 m,y = 2.0 m; its velocity at that time is v = -20 m/s   .If you are at the origin,what do you measure as the magnitude of the magnetic field due to this moving point charge?

Accepted Answer

A) 6.8 pT 
B) 1.1 pT 
C) 5.6 pT 
D) 2.2 pT 
E) 4.4 pT 
A) 6.8 pT 
B) 1.1 pT 
C) 5.6 pT 
D) 2.2 pT 
E) 4.4 pT

Question 5

If m = mB (in a paramagnetic material)for an external magnetic field of 20 kG,what fraction of the saturation magnetization is M at 400 K?

Accepted Answer

A) 5.60 $\times$ 10-4  
B) 2.24 $\times$ 10-3  
C) 1.12 $\times$ 10-3  
D) 3.36 $\times$ 10-3  
E) 4.48 $\times$ 10-1  
A) 5.60 $\times$ 10-4  
B) 2.24 $\times$ 10-3  
C) 1.12 $\times$ 10-3  
D) 3.36 $\times$ 10-3  
E) 4.48 $\times$ 10-1

Question 6

A wire of radius 0.6 cm carries a current of 10 A that is uniformly distributed over its cross section.Calculate the magnetic field strength at r = 0.3 cm divided by that at r = 0.9 cm.

Accepted Answer

A) 1.0 
B) 0.75 
C) 0.50 
D) 2.0 
E) 3.0 
A) 1.0 
B) 0.75 
C) 0.50 
D) 2.0 
E) 3.0

Question 7

A tightly wound solenoid is 15 cm long,has 350 turns,carries a current of 3.0 A,and has an aluminum core ($\chi$m = 2.3 $\times$ 10-5).If you ignore end effects,you will find that the value of the magnetization M at the center is approximately

Accepted Answer

A) 16 mA/m 
B) 8.8 mA/m 
C) 1.8 mA/m 
D) 24 mA/m 
E) 6.2 mA/m 
A) 16 mA/m 
B) 8.8 mA/m 
C) 1.8 mA/m 
D) 24 mA/m 
E) 6.2 mA/m

Question 8

Use the following to answer the next question:  
-Two long parallel wires are a distance d apart (d = 6 cm)and carry equal and opposite currents of 5 A.Point P is distance d from each of the wires.Calculate the magnitude of the magnetic field strength at point P.

Accepted Answer

A) 2.9 $\times$ 10-5 T 
B) 8.5 $\times$ 10-6 T 
C) 3.3 $\times$ 10-5 T 
D) 1.7 $\times$ 10-5 T 
E) none of the above 
A) 2.9 $\times$ 10-5 T 
B) 8.5 $\times$ 10-6 T 
C) 3.3 $\times$ 10-5 T 
D) 1.7 $\times$ 10-5 T 
E) none of the above

Question 9

A wire of radius 0.35 cm carries a current of 75 A that is uniformly distributed over its cross-sectional area.The magnetic field   at the surface of the wire is approximately

Accepted Answer

A) 8.4 mT 
B) 4.3 mT 
C) 6.7 mT 
D) 2.3 mT 
E) 5.7 mT 
A) 8.4 mT 
B) 4.3 mT 
C) 6.7 mT 
D) 2.3 mT 
E) 5.7 mT

Question 10

In a simple picture of the hydrogen atom,the electron moves in circular orbits around the central proton attracted by the Coulomb force.The lowest (n = 1)energy orbit that is allowed for the electron is at a radius of 5.29 $\times$ 10-11 m and the second (n = 2)lowest allowed orbit is at 4 times this radius.Calculate the magnetic field strength at the proton due to the orbital motion of the electron in the n = 2 state.

Accepted Answer

A) 0 T 
B) 6.3 T 
C) 0.39 T 
D) 12.5 T 
E) None of the above 
A) 0 T 
B) 6.3 T 
C) 0.39 T 
D) 12.5 T 
E) None of the above

Question 11

Diamagnetic materials

Accepted Answer

A) have small negative values of magnetic susceptibility. 
B) are those in which the magnetic moments of all electrons in each atom cancel. 
C) experience a small induced magnetic moment when placed in an external magnetic field. 
D) exhibit the property of diamagnetism independently of temperature. 
E) are described by all of the above. 
A) have small negative values of magnetic susceptibility. 
B) are those in which the magnetic moments of all electrons in each atom cancel. 
C) experience a small induced magnetic moment when placed in an external magnetic field. 
D) exhibit the property of diamagnetism independently of temperature. 
E) are described by all of the above.

Question 12

What is the magnetic field at the center of a circular loop with a diameter of 15.0 cm that carries a current of 1.50 A?

Accepted Answer

A) zero 
B) 6.28 $\times$ 10-6 T 
C) 1.26 $\times$  10-5 T 
D) 2.51 $\times$  10-5 T 
E) 1.68 $\times$ 10-4 T 
A) zero 
B) 6.28 $\times$ 10-6 T 
C) 1.26 $\times$  10-5 T 
D) 2.51 $\times$  10-5 T 
E) 1.68 $\times$ 10-4 T

Question 13

If the magnetic susceptibility of a material is positive,

Accepted Answer

A) paramagnetic effects must be greater than diamagnetic effects. 
B) diamagnetic effects must be greater than paramagnetic effects. 
C) diamagnetic effects must be greater than ferromagnetic effects. 
D) ferromagnetic effects must be greater than paramagnetic effects. 
E) paramagnetic effects must be greater than ferromagnetic effects. 
A) paramagnetic effects must be greater than diamagnetic effects. 
B) diamagnetic effects must be greater than paramagnetic effects. 
C) diamagnetic effects must be greater than ferromagnetic effects. 
D) ferromagnetic effects must be greater than paramagnetic effects. 
E) paramagnetic effects must be greater than ferromagnetic effects.

Question 14

A coaxial cable consists of a solid inner cylindrical conductor of radius 2 mm and an outer cylindrical shell of inner radius 3 mm and outer radius 3.5 mm.A current of 15 A flows down the inner wire and an equal return current flows in the outer conductor.If we assume that the currents are uniform over the cross section of the conductors,then calculate the magnitude of the enclosed current for use in Ampere's Law at a radius of 3.25 mm.

Accepted Answer

A) 7.2 A 
B) 3.8 A 
C) 7.8 A 
D) 11.2 A 
E) 7.5 A 
A) 7.2 A 
B) 3.8 A 
C) 7.8 A 
D) 11.2 A 
E) 7.5 A

Question 15

Which of the following statements is false?

Accepted Answer

A) When an electric field is applied to a dielectric,the resultant electric field always decreases. 
B) When a magnetic field is applied to a paramagnetic material,the resultant magnetic field always increases. 
C) When a magnetic field is applied to a diamagnetic material,the resultant magnetic field always decreases. 
D) When a magnetic field is applied to a ferromagnetic material,the resultant magnetic field always increases. 
E) A magnetic dipole can line up parallel or anti-parallel to an applied magnetic field. 
A) When an electric field is applied to a dielectric,the resultant electric field always decreases. 
B) When a magnetic field is applied to a paramagnetic material,the resultant magnetic field always increases. 
C) When a magnetic field is applied to a diamagnetic material,the resultant magnetic field always decreases. 
D) When a magnetic field is applied to a ferromagnetic material,the resultant magnetic field always increases. 
E) A magnetic dipole can line up parallel or anti-parallel to an applied magnetic field.

Question 16

A cylindrical bar magnet of radius 1.0 cm and length 10 cm has a magnetic dipole moment of magnitude m = 2.0 A · m2.What is the magnetic field just outside one end of the magnet?

Accepted Answer

A) 40 mT 
B) 80 mT 
C) 32 mT 
D) 65 mT 
E) 93 mT 
A) 40 mT 
B) 80 mT 
C) 32 mT 
D) 65 mT 
E) 93 mT

Question 17

The magnetic field due to the presence of a charged body

Accepted Answer

A) depends on whether the charged body is moving. 
B) depends on the direction the charged body is moving in relationship to the location of the field point. 
C) varies inversely with the square of the distance between the charged body and the field point. 
D) depends on the magnetic properties of the space between the charged body and the field point. 
E) is described by all of these. 
A) depends on whether the charged body is moving. 
B) depends on the direction the charged body is moving in relationship to the location of the field point. 
C) varies inversely with the square of the distance between the charged body and the field point. 
D) depends on the magnetic properties of the space between the charged body and the field point. 
E) is described by all of these.

Question 18

A cylindrical bar magnet of radius 1.00 cm and length 10.0 cm has a magnetic dipole moment of magnitude m = 2.00 A · m2.What is the magnetization M,assuming it to be uniform in the magnet?

Accepted Answer

A) 2.53 $\times$ 104 A/m 
B) 6.37 $\times$ 104 A/m 
C) 3.18 $\times$ 104 A/m 
D) 1.86 $\times$ 104 A/m 
E) 3.18 $\times$ 102 A/m 
A) 2.53 $\times$ 104 A/m 
B) 6.37 $\times$ 104 A/m 
C) 3.18 $\times$ 104 A/m 
D) 1.86 $\times$ 104 A/m 
E) 3.18 $\times$ 102 A/m

Question 19

A long solenoid with 20 turns per centimeter has a core of iron-silicon.When the current is 1.50 A,the magnetic field inside the core is 4.50 T.The relative permeability Km is approximately

Accepted Answer

A) 1800 
B) 1310 
C) 980 
D) 556 
E) 1190 
A) 1800 
B) 1310 
C) 980 
D) 556 
E) 1190

Question 20

You place a substance in an external magnetic field and find that it is attracted to the field but only to a limited degree because of thermal agitation effects which do not permit atomic dipoles to align completely with the field.You know,therefore,that this substance is

Accepted Answer

A) diamagnetic 
B) paramagnetic 
C) permamagnetic 
D) ferromagnetic 
E) antimagnetic 
A) diamagnetic 
B) paramagnetic 
C) permamagnetic 
D) ferromagnetic 
E) antimagnetic

Exam 27: Sources of the Magnetic Field

Ampère's law is valid

The electron orbiting a proton in a hydrogen atom has a speed of v = 2.19 ×\times× 106 m/s.The magnetic moment of the electron when it is orbiting at the Bohr's radius (= 0.529 nm)is

Nickel has a density of 8.70 g/cm3 and a molecular mass of 58.7 g/mol.Its magnetic moment is 0.587 Bohr magnetons (1 Bohr magneton = 9.27 ×\times× 10-24 A · m2).What is its saturation magnetization?

At a certain instant of time a particle with charge q = 25 μ\muμ C is located at x = 4.0 m,y = 2.0 m; its velocity at that time is v = -20 m/s .If you are at the origin,what do you measure as the magnitude of the magnetic field due to this moving point charge?

If m = mB (in a paramagnetic material)for an external magnetic field of 20 kG,what fraction of the saturation magnetization is M at 400 K?

A wire of radius 0.6 cm carries a current of 10 A that is uniformly distributed over its cross section.Calculate the magnetic field strength at r = 0.3 cm divided by that at r = 0.9 cm.

A tightly wound solenoid is 15 cm long,has 350 turns,carries a current of 3.0 A,and has an aluminum core ( χ\chiχ m = 2.3 ×\times× 10-5).If you ignore end effects,you will find that the value of the magnetization M at the center is approximately

Use the following to answer the next question: -Two long parallel wires are a distance d apart (d = 6 cm)and carry equal and opposite currents of 5 A.Point P is distance d from each of the wires.Calculate the magnitude of the magnetic field strength at point P.

A wire of radius 0.35 cm carries a current of 75 A that is uniformly distributed over its cross-sectional area.The magnetic field at the surface of the wire is approximately

Diamagnetic materials

What is the magnetic field at the center of a circular loop with a diameter of 15.0 cm that carries a current of 1.50 A?

If the magnetic susceptibility of a material is positive,

Which of the following statements is false?

A cylindrical bar magnet of radius 1.0 cm and length 10 cm has a magnetic dipole moment of magnitude m = 2.0 A · m2.What is the magnetic field just outside one end of the magnet?

The magnetic field due to the presence of a charged body

A cylindrical bar magnet of radius 1.00 cm and length 10.0 cm has a magnetic dipole moment of magnitude m = 2.00 A · m2.What is the magnetization M,assuming it to be uniform in the magnet?

A long solenoid with 20 turns per centimeter has a core of iron-silicon.When the current is 1.50 A,the magnetic field inside the core is 4.50 T.The relative permeability Km is approximately

You place a substance in an external magnetic field and find that it is attracted to the field but only to a limited degree because of thermal agitation effects which do not permit atomic dipoles to align completely with the field.You know,therefore,that this substance is

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The electron orbiting a proton in a hydrogen atom has a speed of v = 2.19 $\times$ 10⁶ m/s.The magnetic moment of the electron when it is orbiting at the Bohr's radius (= 0.529 nm)is

Nickel has a density of 8.70 g/cm³ and a molecular mass of 58.7 g/mol.Its magnetic moment is 0.587 Bohr magnetons (1 Bohr magneton = 9.27 $\times$ 10^-24 A · m²).What is its saturation magnetization?

If m = m_B (in a paramagnetic material)for an external magnetic field of 20 kG,what fraction of the saturation magnetization is M at 400 K?

A tightly wound solenoid is 15 cm long,has 350 turns,carries a current of 3.0 A,and has an aluminum core ( $\chi$ _m = 2.3 $\times$ 10^-5).If you ignore end effects,you will find that the value of the magnetization M at the center is approximately

A cylindrical bar magnet of radius 1.0 cm and length 10 cm has a magnetic dipole moment of magnitude m = 2.0 A · m².What is the magnetic field just outside one end of the magnet?

A cylindrical bar magnet of radius 1.00 cm and length 10.0 cm has a magnetic dipole moment of magnitude m = 2.00 A · m².What is the magnetization M,assuming it to be uniform in the magnet?

A long solenoid with 20 turns per centimeter has a core of iron-silicon.When the current is 1.50 A,the magnetic field inside the core is 4.50 T.The relative permeability K_m is approximately