KFUPM-Physics102-032

Dr.Aljalal

Sec07

Sec08

Sec09

Recitation ch 30

Answers at the end

Question 1

Which of the following statements is CORRECT ?

a It is impossible for a constant magnetic field to change

the speed of a charged particle.

b A magnetic field exerts a force on an electron at rest.

c The magnetic field at the center of a current carrying

conducting tube is non-zero.

d An emf can be induced by a constant magnetic field in a

fixed conducting loop.

e The magnetic field inside an ideal solenoid depends on

the radius of the solenoid.

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Question 2

A cylindrical conductor of radius R = 2.50 cm carries a

current of I = 2.50 A along its length. This currents is

uniformly distributed throughout the cross section of

the conductor.

Calculate the magnitude of the magnetic field at a point

that is 1.25 cm from the axis of the conductor.

a 20.0 microTesla

b zero

c 8.00 microTesla

d 10.0 microTesla

e 15.3 microTesla

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Question 3

Consider two solenoids, A and B, having the same current.

Solenoid B has twice the radius and six times the number

of turns per unit length as solenoid A. The ratio of

the magnetic field in the interior of solenoid B to that

in the interior of solenoid A is:

a 6.

b 4.

c 3.

d 2 .

e 1.

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Question 4

Solenoid 2 has twice the radius and 20 times the number of

turns per unit length as solenoid 1. If the current in

solenoid 2 is one fifth (1/5) the current in solenoid 1,

then the ratio of the magnetic field in the interior of

2 to that in the interior of 1 is:

a 4

b 1/4

c 20

d 1/5

e 5

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Question 5

Three parallel wires lie in the xy-plane. The separation

between adjacent wires is 0.1 m, and each wire carries a

10-A current in the same direction. Find the magnitude

of the net force per unit length on one of the outer wires.

a 5.0*10**(-7) N/m.

b 6.0*10**(-4) N/m.

c 1.1*10**(-4) N/m.

d 7.5*10**(-4) N/m.

e 3.0*10**(-4) N/m.

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Question 6

Consider the current-carrying loop shown in figure 9 with

a = 10.0 cm, b = 5.00 cm, theta = 60.0 degrees and I = 0.200 A.

Find the magnitude and direction of the magnetic field at P.

a 5.32*10**(-7) T into the page

b 2.09*10**(-7) T out of the page

c 6.98*10**(-7) T out of the page

d 4.18*10**(-7) T into the page

e 6.28*10**(-7) T out of the page

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Question 7

Four long straight wires carry equal currents into page

as shown in Figure 6. The magnetic force exerted on wire

“A” is:

a East.

b South.

c North.

d Zero.

e West.

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Question 8

Three long wires parallel to the y-axis carry currents

as shown in figure 8.

If I = 10 A, find the magnetic field at the origin.

a zero

b 5.0 micro-Tesla out of the page

c 12 micro-Tesla out of the page

d 5.0 micro-Tesla into the page

e 12 micro-Tesla into the page

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Question 9

Solenoid 2 has twice the radius and six times the number of

turns per unit length as solenoid 1. If they have the same

current, then the ratio of the magnetic field in the interior

of 2 to that in the interior of 1 is:

a 3.

b 6.

c 1/3.

d 2.

e 12.

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Question 10

Two parallel wires, carrying equal currents of 10 A, attract

each other with a force F. If both currents are doubled,

and the distance between them reduced by 50%, the new force

will be:

a F/4.

b 4*F.

c 8*F.

d 16*F.

e F.

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Question 11

A circular loop of radius 0.1 m has a resistance of 6 Ohms.

If it is attached to a 12 V battery, how large a magnetic

field is produced at the center of the loop?

a 3.0*10**(-5) T.

b 5.2*10**(-5) T.

c 0.5*10**(-5) T.

d zero.

e 1.3*10**(-5) T.

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Question 12

The segment of wire is formed into the shape as shown in

Figure 7 and carries a current I = 6 A. When R = 6.28 cm,

what is the magnetic field at the point P?

a 3.0*10**(-5) T into the page.

b 6.1*10**(-5) T into the page.

c Zero.

d 6.1*10**(-5) T out of the page.

e 3.0*10**(-5) T out of the page.

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Question 13

Four long conducting wires are parallel to each other.

Their cross sections form the corners of a square of

side a = 15 cm. The directions of the currents are as

shown in figure 10. The magnitude of the current in

each wire is 15 A. What is the magnitude of the magnetic

field at the center of the square ?

a 1.1*10**(-4) T

b 8.4*10**(-5) T

c 5.7*10**(-5) T

d 2.8*10**(-5) T

e zero

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Question 14

Three parallel wires lie parallel to the x-axis as shown in

figure 9. The separation between adjacent wires is 1.0 m,

and each wire carries a 20-A current. Find the magnitude of

the net force per unit length on wire 2 due to wires 1 & 3.

a 7.5*10**(-4) N

b 80*10**(-6) N

c 4.6*10**(-4) N

d 16*10**(-5) N

e zero

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Question 15

Which one of the following statements is True?

a If the current in each of two parallel current-carrying

wires is doubled, the force between them will be doubled.

b The torque on a magnetic dipole is zero when it is in a

uniform magnetic field.

c A uniform magnetic field can be found at the center of a

solenoid.

d The magnetic field is smallest where the field lines are

closest.

e The magnetic field due to a long straight wire increases with

increasing distance from the wire.

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Question 16

Figure (10) shows four long straight wires passing through

the plane of the paper. They are fixed at the corners of a

square of diagonal 2.0 cm. Each wire carries a current of

2 A. Three of them are out of the paper and one is into the

paper. The magnitude of the magnetic field at the center

"C" of the square has magnitude:

a zero.

b 5.1*10**(-6) T.

c 8.0*10**(-5) T.

d 3.0*10**(-5) T.

e 1.0*10**(-5) T.

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Question 17

A solid cylindrical conducting wire has a radius of 15 cm.

An electric current is uniformly distributed over the

wire with a current density of 1.0*10**4 A/m**2.

What is the magnitude of the magnetic field at a point

5.0 cm from the axis of the wire ?

a 9.0*10**(-4) T

b 7.5*10**(-4) T

c 6.3*10**(-4) T

d 3.1*10**(-4) T

e zero

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Answers

1 a

2 d

3 a

4 a

5 e

6 b

7 a

8 b

9 b

10 c

11 e

12 a

13 e

14 e

15 c

16 c

17 d