Question 1

The force per unit length between two current-carrying wires is expressed as
F/l = ($\mu$0/2 $\pi$d)I2
Where I is the current, d the separation of the wires, and l the length of each wire. A plot of force per unit length versus I2 gives a straight line, the slope of which is

Accepted Answer

A)  $\mu$0  
B)  F/l 
C)  (2 $\pi$d/$\mu$0)1/2  
D) $\mu$0/2 $\pi$d 
E)  FI2/l

Question 2

Use the following to answer the next question: 
-Two long parallel wires are a distance d apart and carry equal and opposite currents. Point P is distance d from each of the wires. Which diagram best represents the direction of the magnetic field at point P?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 3

A solenoid carries a current I. An electron is injected with velocity  along the axis AB of the solenoid. When the electron is at C, it experiences a force that is

Accepted Answer

A)  zero. 
B)  not zero and along AB. 
C)  not zero and along BA. 
D)  not zero and perpendicular to the page. 
E)  None of these is correct.

Question 4

Two long, parallel wires are spaced 1 m apart in air, and you have established a current of 1 A in each. The force per unit length that each wire exerts on the other is approximately

Accepted Answer

A)  2 * 10-6 N/m 
B)  2 * 10-5 N/m 
C)  2 * 10-7 N/m 
D)  2 $\pi$* 10-5 N/m 
E)  2 $\pi$ * 10-6 N/m

Question 5

The magnetic field at a distance of 50 cm from a long, straight wire carrying a current of 5.0 A is approximately

Accepted Answer

A)  10 $\mu$T 
B)  50 $\mu$T 
C)  5.0 $\mu$T 
D)  32 $\mu$T 
E)  2.0 $\mu$T

Question 6

If m = mB in a paramagnetic material (mB = 9.27* 10-24 J/T), at what temperature is the magnetization 3% of the saturation magnetization in an applied magnetic field of
1)00 T?

Accepted Answer

A)  12.8 K 
B)  7.46 K 
C)  22.4 K 
D)  67.2 K 
E)  3.73 K

Question 7

Two long, straight parallel wires 7.6 cm apart carry currents of equal magnitude I. They attract each other with a force per unit length of 4.3 nN/m. The current I is approximately

Accepted Answer

A)  1.6 mA 
B)  40 mA 
C)  37 mA 
D)  59 mA 
E)  4.0 mA

Question 8

A long solenoid is wound around a titanium core ($\chi$m = 7.06 * 10-5) and carries a current. If the core is removed while the current is held constant, the magnetic field inside the solenoid

Accepted Answer

A)  remains constant. 
B)  increases by approximately 0.004%. 
C)  decreases by approximately 0.007%. 
D)  increases by approximately 0.007%. 
E)  decreases by approximately 0.004%.

Question 9

When a sample is inserted into a solenoid carrying a constant current, the magnetic field inside the solenoid increases by 0.005%. What is the magnetic susceptibility of the sample?

Accepted Answer

A)  -5 * 10-5  
B)  +5* 10-5  
C)  3.6 * 10-5  
D)  -3.6 * 10-5  
E)  More information is needed to answer this question.

Question 10

The graph that best represents the magnetic field B between the coils of radius R of a Helmholtz pair as a function of distance along the axis of the pair is

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 11

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 a distance of 5.0 cm from the center of the wire is approximately

Accepted Answer

A)  0.47 mT 
B)  1.5 mT 
C)  0.30 mT 
D)  0.56 mT 
E)  0.24 mT

Question 12

A tightly wound solenoid is 15 cm long, has 350 turns, and carries a current of 3.0 A. If you ignore end effects, you will find that the value of  at the center of the solenoid when there is an iron core of magnetization M = 1.4 * 106 A/m is approximately

Accepted Answer

A)  11 mT 
B)  8.8 mT 
C)  1.8 mT 
D)  7.0 mT 
E)  6.2 mT

Question 13

A wire carries an electric current straight upward. What is the direction of the magnetic field due to the current north of the wire?

Accepted Answer

A)  north 
B)  east 
C)  west 
D)  south 
E)  upward

Question 14

A long solenoid with 15 turns per centimeter has a core of annealed iron. When the current is 1.00 A, the magnetic field inside the iron core is 2.46 T. The magnetization M is approximately

Accepted Answer

A)  1.80 * 10-4 A/m 
B)  1.31 *106 A/m 
C)  1.96 *106 A/m 
D)  5.56 *10-4 A/m 
E)  1.50 *104 A/m

Question 15

A long solenoid with 15 turns per centimeter has a core of annealed iron. When the current is 1.00 A, the magnetic field inside the iron core is 2.46 T. The applied field  app is approximately

Accepted Answer

A)  18.8 $\mu$T 
B)  2.46 T 
C)  4.32 mT 
D)  3.87 T 
E)  1.88 mT

Question 16

Calculate the magnetic field at the center of a circular current loop of area 0.200 m2 divided by the magnetic field at the center of a square current loop of the same inside area for the same current I value.

Accepted Answer

A)  1.00 
B)  1.02 
C)  0.246 
D)  0.985 
E)  0.785

Question 17

Two straight wires perpendicular to the plane of this page are shown in the figure. The currents in the wires are the same. The current in M is into the page and the current in N is out of the page. The vector that represents the resultant magnetic field at point P is

Accepted Answer

A)   
B)   
C)   
D)   
E)  None of these is correct.

Question 18

The Biot-Savart law is similar to Coulomb's law in that both

Accepted Answer

A)  are inverse square laws. 
B)  include the permeability of free space. 
C)  deal with excess charges. 
D)  are not electrical in nature. 
E)  are described by none of the above.

Question 19

A long straight wire of radius R carries a current density J = kr A/m2 where k is a constant. The magnetic field for r < R is (Hint: Current enclosed  .)

Accepted Answer

A)  $\mu$0kr2/2 
B)  $\mu$0kr2/3 
C)  2 $\pi$$\mu$0kr 
D)  2 $\pi$$\mu$0kr/2 
E)  none of the above

Question 20

If you assume that the scalings of the axes of these hysteresis curves are the same, you can conclude that

Accepted Answer

A)  curve 1 is for a magnetically soft material. 
B)  curve 2 is for a magnetically soft material. 
C)  curve 2 is for a magnetically hard material. 
D)  both curves are for a magnetically soft material. 
E)  both curves are for a magnetically hard material.

Exam 7: Sources of the Magnetic Field

The force per unit length between two current-carrying wires is expressed as F/l = ( $\mu$ ₀/2 $\pi$ d) I² Where I is the current, d the separation of the wires, and l the length of each wire. A plot of force per unit length versus I² gives a straight line, the slope of which is

Use the following to answer the next question: -Two long parallel wires are a distance d apart and carry equal and opposite currents. Point P is distance d from each of the wires. Which diagram best represents the direction of the magnetic field at point P?

A solenoid carries a current I. An electron is injected with velocity along the axis AB of the solenoid. When the electron is at C, it experiences a force that is

Two long, parallel wires are spaced 1 m apart in air, and you have established a current of 1 A in each. The force per unit length that each wire exerts on the other is approximately

The magnetic field at a distance of 50 cm from a long, straight wire carrying a current of 5.0 A is approximately

If m = m_B in a paramagnetic material (m_B = 9.27* 10^-24 J/T) , at what temperature is the magnetization 3% of the saturation magnetization in an applied magnetic field of 1) 00 T?

Two long, straight parallel wires 7.6 cm apart carry currents of equal magnitude I. They attract each other with a force per unit length of 4.3 nN/m. The current I is approximately

A long solenoid is wound around a titanium core ( $\chi$ _m = 7.06 * 10^-5) and carries a current. If the core is removed while the current is held constant, the magnetic field inside the solenoid

When a sample is inserted into a solenoid carrying a constant current, the magnetic field inside the solenoid increases by 0.005%. What is the magnetic susceptibility of the sample?

The graph that best represents the magnetic field B between the coils of radius R of a Helmholtz pair as a function of distance along the axis of the pair is

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 a distance of 5.0 cm from the center of the wire is approximately

A tightly wound solenoid is 15 cm long, has 350 turns, and carries a current of 3.0 A. If you ignore end effects, you will find that the value of at the center of the solenoid when there is an iron core of magnetization M = 1.4 * 10⁶ A/m is approximately

A wire carries an electric current straight upward. What is the direction of the magnetic field due to the current north of the wire?

A long solenoid with 15 turns per centimeter has a core of annealed iron. When the current is 1.00 A, the magnetic field inside the iron core is 2.46 T. The magnetization M is approximately

Calculate the magnetic field at the center of a circular current loop of area 0.200 m² divided by the magnetic field at the center of a square current loop of the same inside area for the same current I value.

Two straight wires perpendicular to the plane of this page are shown in the figure. The currents in the wires are the same. The current in M is into the page and the current in N is out of the page. The vector that represents the resultant magnetic field at point P is

The Biot-Savart law is similar to Coulomb's law in that both

If you assume that the scalings of the axes of these hysteresis curves are the same, you can conclude that

Exam 7: Sources of the Magnetic Field

The force per unit length between two current-carrying wires is expressed as F/l = ( μ\muμ 0/2 π\piπ d) I2 Where I is the current, d the separation of the wires, and l the length of each wire. A plot of force per unit length versus I2 gives a straight line, the slope of which is

Use the following to answer the next question: -Two long parallel wires are a distance d apart and carry equal and opposite currents. Point P is distance d from each of the wires. Which diagram best represents the direction of the magnetic field at point P?

A solenoid carries a current I. An electron is injected with velocity along the axis AB of the solenoid. When the electron is at C, it experiences a force that is

Two long, parallel wires are spaced 1 m apart in air, and you have established a current of 1 A in each. The force per unit length that each wire exerts on the other is approximately

The magnetic field at a distance of 50 cm from a long, straight wire carrying a current of 5.0 A is approximately

If m = mB in a paramagnetic material (mB = 9.27* 10-24 J/T) , at what temperature is the magnetization 3% of the saturation magnetization in an applied magnetic field of 1) 00 T?

Two long, straight parallel wires 7.6 cm apart carry currents of equal magnitude I. They attract each other with a force per unit length of 4.3 nN/m. The current I is approximately

A long solenoid is wound around a titanium core ( χ\chiχ m = 7.06 * 10-5) and carries a current. If the core is removed while the current is held constant, the magnetic field inside the solenoid

When a sample is inserted into a solenoid carrying a constant current, the magnetic field inside the solenoid increases by 0.005%. What is the magnetic susceptibility of the sample?

The graph that best represents the magnetic field B between the coils of radius R of a Helmholtz pair as a function of distance along the axis of the pair is

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 a distance of 5.0 cm from the center of the wire is approximately

A tightly wound solenoid is 15 cm long, has 350 turns, and carries a current of 3.0 A. If you ignore end effects, you will find that the value of at the center of the solenoid when there is an iron core of magnetization M = 1.4 * 106 A/m is approximately

A wire carries an electric current straight upward. What is the direction of the magnetic field due to the current north of the wire?

A long solenoid with 15 turns per centimeter has a core of annealed iron. When the current is 1.00 A, the magnetic field inside the iron core is 2.46 T. The magnetization M is approximately

A long solenoid with 15 turns per centimeter has a core of annealed iron. When the current is 1.00 A, the magnetic field inside the iron core is 2.46 T. The applied field app is approximately

Calculate the magnetic field at the center of a circular current loop of area 0.200 m2 divided by the magnetic field at the center of a square current loop of the same inside area for the same current I value.

Two straight wires perpendicular to the plane of this page are shown in the figure. The currents in the wires are the same. The current in M is into the page and the current in N is out of the page. The vector that represents the resultant magnetic field at point P is

The Biot-Savart law is similar to Coulomb's law in that both

A long straight wire of radius R carries a current density J = kr A/m2 where k is a constant. The magnetic field for r < R is (Hint: Current enclosed .)

If you assume that the scalings of the axes of these hysteresis curves are the same, you can conclude that

The force per unit length between two current-carrying wires is expressed as F/l = ( $\mu$ ₀/2 $\pi$ d) I² Where I is the current, d the separation of the wires, and l the length of each wire. A plot of force per unit length versus I² gives a straight line, the slope of which is

If m = m_B in a paramagnetic material (m_B = 9.27* 10^-24 J/T) , at what temperature is the magnetization 3% of the saturation magnetization in an applied magnetic field of 1) 00 T?

A long solenoid is wound around a titanium core ( $\chi$ _m = 7.06 * 10^-5) and carries a current. If the core is removed while the current is held constant, the magnetic field inside the solenoid

A tightly wound solenoid is 15 cm long, has 350 turns, and carries a current of 3.0 A. If you ignore end effects, you will find that the value of at the center of the solenoid when there is an iron core of magnetization M = 1.4 * 10⁶ A/m is approximately

Calculate the magnetic field at the center of a circular current loop of area 0.200 m² divided by the magnetic field at the center of a square current loop of the same inside area for the same current I value.