Question 1

A long solenoid (n = 80 turns/cm)carries a current of 70 mA.Determine the magnitude of the magnetic field inside the solenoid.

Accepted Answer

7.0 gauss

Question 2

What current in a solenoid 15.0-cm long wound with 100 turns would produce a magnetic field equal to that of the Earth,5.00 × 10−5 T?

Accepted Answer

59.7 mA

Question 3

A long wire lies in a tangle on the surface of a table,as shown below.When a current is run through the wire as shown,the largest component of the magnetic field at X points

Accepted Answer

A) into the table. 
B) out of the table. 
C) parallel to the nearest segment of wire. 
D) antiparallel to the nearest segment of wire. 
E) along a circle which has its center at the center of the overall loop. 
A) into the table. 
B) out of the table. 
C) parallel to the nearest segment of wire. 
D) antiparallel to the nearest segment of wire. 
E) along a circle which has its center at the center of the overall loop. B

Question 4

Two long parallel wires separated by 5.0 mm each carry a current of 60 A.These two currents are oppositely directed.What is the magnitude of the magnetic field at a point that is between the two wires and 2.0 mm from one of the two wires?

Accepted Answer

A) 2.0 mT 
B) 10 mT 
C) 8.0 mT 
D) 1.6 mT 
E) 7.2 mT 
A) 2.0 mT 
B) 10 mT 
C) 8.0 mT 
D) 1.6 mT 
E) 7.2 mT

Question 5

If a = 2.0 cm,b = 5.0 cm,and I = 20 A,what is the magnitude of the magnetic field at the point P?

Accepted Answer

A) 4.5 μT 
B) 7.5 μT 
C) 9.0 μT 
D) 6.0 μT 
E) 3.6 μT 
A) 4.5 μT 
B) 7.5 μT 
C) 9.0 μT 
D) 6.0 μT 
E) 3.6 μT

Question 6

What is the magnitude of the magnetic field at point P if a = R and b = 2R?

Accepted Answer

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

Question 7

The field at (0,0,1.0 m)is in the negative y direction.

Accepted Answer

A) 3 and 4 
B) 1 and 3 
C) 2 and 4 
D) 1 and 2 
E) None of these 
A) 3 and 4 
B) 1 and 3 
C) 2 and 4 
D) 1 and 2 
E) None of these

Question 8

In the figure,if a = 2.0 cm,b = 4.0 cm,and I = 2.0 A,what is the magnitude of the magnetic field at point P?

Accepted Answer

A) 49 μT 
B) 39 μT 
C) 50 μT 
D) 69 μT 
E) 13 μT 
A) 49 μT 
B) 39 μT 
C) 50 μT 
D) 69 μT 
E) 13 μT

Question 9

The following statements all refer to the human brain when mental activity is occurring.Which statement is correct?

Accepted Answer

A) In order to detect electric currents in the brain,you must open the skull and make direct electrical contact with the brain. 
B) The electric currents in the brain can be detected outside the brain by detecting the magnetic fields they produce. 
C) The electric currents in the brain can be mapped by shaving a person's head and dropping iron filings on the head. 
D) The electric currents in the brain produce an aura that can be detected visually. 
E) The electric currents in the brain cannot be detected by any means. 
A) In order to detect electric currents in the brain,you must open the skull and make direct electrical contact with the brain. 
B) The electric currents in the brain can be detected outside the brain by detecting the magnetic fields they produce. 
C) The electric currents in the brain can be mapped by shaving a person's head and dropping iron filings on the head. 
D) The electric currents in the brain produce an aura that can be detected visually. 
E) The electric currents in the brain cannot be detected by any means.

Question 10

If a = 1.0 cm,b = 3.0 cm,and I = 30 A,what is the magnitude of the magnetic field at point P?

Accepted Answer

A) 0.62 mT 
B) 0.59 mT 
C) 0.35 mT 
D) 0.31 mT 
E) 0.10 mT 
A) 0.62 mT 
B) 0.59 mT 
C) 0.35 mT 
D) 0.31 mT 
E) 0.10 mT

Question 11

A long hollow cylindrical conductor (inner radius = 2.0 mm,outer radius = 4.0 mm)carries a current of 24 A distributed uniformly across its cross section.A long wire which is coaxial with the cylinder carries an equal current in the opposite direction.What is the magnitude of the magnetic field 3.0 mm from the axis?

Accepted Answer

A) 0.82 mT 
B) 0.93 mT 
C) 0.70 mT 
D) 0.58 mT 
E) 0.40 mT 
A) 0.82 mT 
B) 0.93 mT 
C) 0.70 mT 
D) 0.58 mT 
E) 0.40 mT

Question 12

The field at (1.0 m,0,0)is zero.

Accepted Answer

To provide a full answer to the input qu

Question 13

Three long,straight,parallel wires all lie in the yz plane and each carries a current of 20 A in the positive z direction.The two outer wires are each 4.0 cm from the center wire.What is the magnitude of the magnetic force on a 50-cm length of either of the outer wires?

Accepted Answer

A) 1.0 mN 
B) 0.50 mN 
C) 1.1 mN 
D) 1.5 mN 
E) 2.0 mN 
A) 1.0 mN 
B) 0.50 mN 
C) 1.1 mN 
D) 1.5 mN 
E) 2.0 mN

Question 14

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

Accepted Answer

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

Question 15

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

Accepted Answer

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

Question 16

A long straight wire carries a current of 40 A in a region where a uniform external magnetic field has a 30-μT magnitude and is parallel to the current.What is the magnitude of the resultant magnetic field at a point that is 20 cm from the wire?

Accepted Answer

A) 70 μT 
B) 40 μT 
C) 10 μT 
D) 50 μT 
E) 36 μT 
A) 70 μT 
B) 40 μT 
C) 10 μT 
D) 50 μT 
E) 36 μT

Question 17

Two long parallel wires are separated by 6.0 mm.The current in one of the wires is twice the other current.If the magnitude of the force on a 3.0-m length of one of the wires is equal to 8.0 μN,what is the greater of the two currents?

Accepted Answer

A) 0.20 A 
B) 0.40 A 
C) 40 mA 
D) 20 mA 
E) 0.63 A 
A) 0.20 A 
B) 0.40 A 
C) 40 mA 
D) 20 mA 
E) 0.63 A

Question 18

Each of two parallel wires separated by 6.0 mm carries a 40-A current.These two currents are in the same direction.Determine the magnitude of the magnetic field at a point that is 5.0 mm from each of the wires.

Accepted Answer

A) 2.6 mT 
B) zero 
C) 1.9 mT 
D) 1.6 mT 
E) 3.2 mT 
A) 2.6 mT 
B) zero 
C) 1.9 mT 
D) 1.6 mT 
E) 3.2 mT

Question 19

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

Accepted Answer

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. 
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.

Question 20

The planetary model of the hydrogen atom consists of an electron in a circular orbit about a proton.The motion of the electron of charge 1.60 × 10−19 C creates an electric current.The radius of the electron orbit is 5.30 × 10−11 m and the electron's velocity is 2.20 × 106 m/s.What is the magnetic field strength at the location of the proton?

Accepted Answer

Exam 30: Sources of the Magnetic Field

A long solenoid (n = 80 turns/cm)carries a current of 70 mA.Determine the magnitude of the magnetic field inside the solenoid.

What current in a solenoid 15.0-cm long wound with 100 turns would produce a magnetic field equal to that of the Earth,5.00 × 10−5 T?

A long wire lies in a tangle on the surface of a table,as shown below.When a current is run through the wire as shown,the largest component of the magnetic field at X points

Two long parallel wires separated by 5.0 mm each carry a current of 60 A.These two currents are oppositely directed.What is the magnitude of the magnetic field at a point that is between the two wires and 2.0 mm from one of the two wires?

If a = 2.0 cm,b = 5.0 cm,and I = 20 A,what is the magnitude of the magnetic field at the point P?

What is the magnitude of the magnetic field at point P if a = R and b = 2R?

The field at (0,0,1.0 m)is in the negative y direction.

In the figure,if a = 2.0 cm,b = 4.0 cm,and I = 2.0 A,what is the magnitude of the magnetic field at point P?

The following statements all refer to the human brain when mental activity is occurring.Which statement is correct?

If a = 1.0 cm,b = 3.0 cm,and I = 30 A,what is the magnitude of the magnetic field at point P?

The field at (1.0 m,0,0)is zero.

Three long,straight,parallel wires all lie in the yz plane and each carries a current of 20 A in the positive z direction.The two outer wires are each 4.0 cm from the center wire.What is the magnitude of the magnetic force on a 50-cm length of either of the outer wires?

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

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 long straight wire carries a current of 40 A in a region where a uniform external magnetic field has a 30-μT magnitude and is parallel to the current.What is the magnitude of the resultant magnetic field at a point that is 20 cm from the wire?

Two long parallel wires are separated by 6.0 mm.The current in one of the wires is twice the other current.If the magnitude of the force on a 3.0-m length of one of the wires is equal to 8.0 μN,what is the greater of the two currents?

Each of two parallel wires separated by 6.0 mm carries a 40-A current.These two currents are in the same direction.Determine the magnitude of the magnetic field at a point that is 5.0 mm from each of the wires.

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What current in a solenoid 15.0-cm long wound with 100 turns would produce a magnetic field equal to that of the Earth,5.00 × 10−⁵ T?