# Q1) The geographic north pole of the earth is magnetically a 1) north pole 2) south pole

Electronics - Devices

Oct 18, 2013 (4 years and 8 months ago)

114 views

Q
1)

The geogra
phic north pole of the earth is
magnetically a

1)

north pole

2)

south pole

Q2)

The magnetic fiel
d of the Earth is useful to us.
Why?

1)

Enables bird
s to navigate long distances

2)

Deflects dangerous particles from the Sun to the poles

3)

Tells us about the interior of the Earth

4)

All of the above

5)

None of the above

Q3
)

Cosmic rays
(atomic nuclei stripped bare of
their electr
ons)
would continuously bombard
Earth’s surface if
most of them were
not deflected
by Ear
th’s magnetic field. Given that
Earth is, t
o an
excellent approximation, a
magnetic dipole, the intensity of
c
osmic
rays
bombarding its surface is greatest at the

1)

poles.

2)

mid
-
latitudes.

3)

equator.

Q
4)

Compared to the huge force that attracts an iron
tack to a strong magnet, the force that the tack exerts on
the magnet is

1)

relatively weak

2)

equally h
uge

3)

Q5
)

At any point the magnetic field lines are in the direction of:

1)

the magnetic force on a moving positive charge

2)

the magnetic force on a moving negative charge

3)

the velocity of a moving positive char
ge

4)

the velocity of a moving negative charge

5)

none of the above

Q6
)

(a)

Can an electron at rest in a magnetic field be set into
motion by the magnetic field?

(b)

Can an electron at rest in
an electric field be set into motion by the electric field?

1)
(a)

yes

(b)

yes

2)
(a)

ye
s

(b)

no

3)
(a)

no

(b)

no

4)
(a)

no

(b)

yes

Q7
)

An electron moves through a region wit
h a constant magnetic
field B.
The work done on the electron by the magnetic field

1
)

is positive.

2
)

is equal to zero.

3
)

is negative.

4
)

can't be calculated with
out more

information.

Q8
)

A charged particle, passing through a certain region of space, has a
velocity whose magnitude and direction remain constant.
(a)

If it is known
that the external magneti
c field is zero everywhere in this region, can you
conclude that the external electric field is also zero?
(b)

If it is know that
the external electric field is zero everywhere, can you conclude that the
external magnetic field is also zero?

1)
(a) yes

(b
) yes

2)
(a) yes

(b) no

3)
(a) no

(b) no

4)
(a) no

(b) yes

Q
9
)

What is the direction of the magnetic force on the
moving charged particle in

each of the three cases below?

1)

(a)

down
(b)

left
(c)

out

2)

(a)

down
(b)

left
(c)

in

3)

(a)

down
(b)

right
(c)

out

4)

(a)

up
(b)

left

(c)

out

5)

(a)

up
(b)

left
(c)

in

B

B

+

B

Case A

Case B

Case C

Q10
)

The figure below shows three situations in which a positive particle
of velocity

moves through a uniform magnetic field
and experiences
a mag
netic force
. In each situation, determine whether the orientations
of the vectors are physically reasonable.

1)

(a)

no
(b)

no
(c)

yes

2)

(a)

no
(b)

yes
(c)

no

3)

(a)

no
(b)

yes
(c)

yes

4)

(a)

yes
(b)

no
(c)

yes

5)

(a)

yes
(b)

no
(c)

no

Q11
)

The figure
shows a uniform magnetic field
B directed to the
lef
t and a wire carrying a current
into the page. The magnetic force
acting on the wire is:

1)

toward the top of the page

2)

toward the bottom of the page

3)

toward the left

4)

toward

the right

5)

zero

Q
1
2)

A beam of electrons is sent horizontally down the axis of a
tube

to strike a fluorescent screen
at the end of the tube. On the
way, the electrons encounter a magnetic field directed
vertically

downward. The spot on the screen will therefore be deflected:

1)

upward

2)

downward

3)

to the right as seen from the electron source

4)

to the left as seen from the electron source

5)

not at all

Q13
)

Two electrons are located in a region of space where the magnetic
field is zero. Electron
A
is at
rest; and electron
B
is moving westward with
a constant velo
city. A non
-
zero magnetic field

directed eastward is then

applied to the
region. In what
direction
, if any, will each electron be
moving after the field is applied?

electron
A

electron
B

1
)

at rest

westward

2
)

northward

eastward

3
)

at rest

eastward

4
)

southward

downward, toward the earth

5
)

upward, awa
y from earth

westward

Q14
)

A positively char
ged particle moves to the right
in a
magnetic
field that points upward. Which
way does the

magnetic
force o
n the particle
point?

1)

Upward

2
)

Downward

3
)

Into the board

4)

Out of the board

5)

There is no force since the velocity and B field are perpendicular

Q15
)

A negatively charge
d particle moves to the left in
a magnetic
fi
eld that points downward. Which
w
ay does the

magnetic force on
the particle
point?

1)

Upward

2)

Into the board

3)

Downward

4)

Out of the board

5)

There is no force since the velocity and B field are perpendicular

Q16
)

In a region of space there is a uniform magnetic field pointing
in the positive z direction. In what direction should a negative
charge move to experience a force in the positive x direction?

1)
In the positive x direction

2)

In the negative x direction

3)

In the positive y direction

4)

In the negative y direction

5)

None of the above

Q17
)

A uniform magnetic field is in the positiv
e z direction. A
positively charged particle is moving

in the positive x direction
through the field. The net force on the particle can be made zero

by applying an electric field in what direction?

1)

Positive y

2)

Negative y

3)

Positive x

4)

Negative x

5
)

Positive z

Q18
)

An electron travels through a region of space with no
accelerat
ion. Which one of the following
statements is the best
conclusion?

1
)

Both E and B
must be zero in that region.

2
)

E must be zero, but B might be non
-
zero in that region.

3
)

E and B might both be non
-
zero, but they must be mutually
perpendicular.

4
)

B must be zero, but E might be non
-
zero in that region.

5
)

E and B might both be non
-
zero
, but they must point in opposite
directions.

Q19
)

A positive particle is released from rest in a reg
ion of space where
there is constant, uniform, electric field
, and a constant, uniform
magnetic field
. The electric field points up and the magnetic field
points out of the page in the diagram below. Which
path will the positive
particle follow? (All paths shown are in plane of the page.)

Q20
)

If a particle move in a region of space that contains crossed
electric and magnetic fields in opposition, the particle will move in
a straight line (that is, neither force dominates the motion) if its
speed is given by v = E/B.

Which of the two forces dominates if
the speed of the particle is v < E/B?

1)

the electric force

2)

the magnetic force

3)

neither force

E

B
(out)

A

B

C

D: it will r
emain stationary

Q2
1
)

A proton traveling due north enters a region that contains
both a magnet
ic field and an electric field.
The electric field lines
point due west. It is observed that the proton co
ntinues to travel in
a straight
line due north. I
n which direction must the magnetic field
lines point?

1
)

up

2
)

down

3
)

east

4
)

west

5
)

south

Q
2
2)

A charged particle moves into a region containing both an electric
and magnetic field. Which of the statements below are true?

A:

The particle cannot accelerate in the direction of B.

B
:

The path of the particle must be a circle.

C
:

Any change in the particle’s kinetic energy is caused by the E field.

1)

Only A

2)

Only B

3)

Only C

4)

Both A&C

5)

All are true.

Q2
3
)

Three particles move through a region of uniform magnetic
field pointed out of the plane and follow the trajectories shown.
The charges on these particles are

1
)

q
1

< 0,
q
2

> 0,
q
3

= 0.

2
)

q
1

> 0,
q
2

= 0,
q
3

< 0.

3
)

q
1

< 0,

q
2

= 0,
q
3

> 0.

4
)

q
1

= 0,
q
2

> 0,
q
3

< 0.

Q2
4)

The figure below shows the path of an electron that passes through
two regions containing uniform magnetic fi
elds of magnitudes B
1

and B
2
.
Its path in each region is a half
-
circle.
(a)

What is the direction of B
1
?

(b)

Is the time spent in region 1 greater than, less than, or the same as the
time spent in region 2?

1)

(a)

into board
(b)

greater than

2)

(a)

into board
(b)

less than

3)

(a)

into board
(b)

the same as

4)

(a)

out of board
(b)

less than

5)

(a)

out of board
(b)

the same as

Q2
5)

An electron moves through a region of uniform magnetic
field of magnitude 60

T, directed along the positiv
e direction of
an x axis. The electron has a velocity of

km/s as it enters
the field. To an observer looking into the magnetic field region
from the entrance point of the electron, does the electron spiral
clockwise or countercl
ockwise as it moves deeper into the region?

1)

clockwise

2)

counterclockwise

Q2
6
)

The figure here shows the circular paths of two particles that

travel
at the same speed in a uniform magnetic field, which is directed into the
page. One particle is a proton; the other is an electron (which is
less
massive).
(a)

Which particle follows the smaller circle, and
(b)

does that
particle travel clockwise or counterclockwise?

1)

(a)

proton

(b)

CW

2)

(a)

proton

(b)
CCW

3)

(a)

electron
(b)

CW

4)

(
a)

electron

(b)

CCW

Q2
7
)

In the following situations a charge q moves in a uniform
magnetic field. The strength of the magnetic field is indicated by
the density of field lines. In all cases the speed of the charge is the
same. For which situation(s) will the charge q travel the greatest
distance in a given time T?

1
)

2

2)

4

3)

5

4)

1 & 3

5)

none of the above

Q2
8
)

The diagram shows a straight wire carrying a flow of
elect
rons into the page. The wire is
between the poles of a
permanent
magnet. The direction of th
e magnetic force exerted on
the
wire is:

1)

right

2)

left

3)

up

4)

down

5)

into the
page

Q29
)

The figure below shows four views of a horseshoe magnet
and a straight wire in which electrons are flowing out of the page,
perpendicular to the plane of the magnet. In
which case will the
magnetic force on the wire be directed upwards?

1)

a

2)

b

3)

c

4)

d

Q30
)

A square loop of wire carrying current I is in a uniform
magnetic field B. The loop is perpendicular to B (B out of the
page). Wh
at is the direction of the net force on the wire?

1)

out of the page

2)

into the page

3)

4)

5)

None of these/don't know

Q
3
1
)

A
rectangu
lar loop is placed in a uniform
magnetic f
ield with
the plane of the loop
perpendicular

to the direction of the field.
If a
current i
s made to fl
ow through the loop
in the sense

shown by the
arrows, the field
exerts on the loop:

1)

a net force.

2)

a net torque.

3)

a net force and a net torque.

4)

neither a net force nor a net torque.

Q
3
2)

A rectangu
lar loop is placed in a uniform

magnetic f
ield
with
the plane of the loop
parallel to the direc
tion of the field. If a
current
to flow through the loop in the
sense shown
by the
arrows, the field exerts
on the loop:

1
)

a net force.

2)

a net torque.

3)

a net force and a net torque.

4)

neither a

net force nor a net torque.

Q33
)

A current loop is pla
ced in a magnetic field as shown below.

The loop tends to

1)

rotate, left side up

2)

rotate, right side up

3)

rotate, bottom side up

4)

rotate, top side up

5)

none of the above
-

it stays in place

Q34
)

The figure below shows four orientations, at angle

, of a magnetic
dipole moment

in a magnetic field. Rank the orientations according to
(a) the magnitude of

the torque on the dipole and (b) the potential energy
of the dipole, greatest first.

1)

(a)

all tie
(b)

all tie

2)

(a)

all tie
(b)

1 & 4, 2 & 3

3)

(a)

all tie
(b)

2 & 3, 1 & 4

4)

(a)

1 & 4, 2 & 3
(b)

all tie

5)

(a)

1 & 4
, 2 & 3
(b)

2 & 3, 1 & 4

Q35
)

If you place a chunk of iron near the south pole of a
magnet, attraction will occur. Will attraction also occur if
you place the iron near the north pole of a magnet?

1)

yes

2)

no

Q36
)

Several pap
er clips dangle from the north pole of a magnet.
The induced pole in the bottom of the lowermost paper clip is a

1)

north pole

2)

south pole

3)

north or south pole

no difference really

Q37
)

What would happen if you heated a bar magnet

1)

Higher temp means faster mot
ion: magnetic strength would
increase

2)

Higher temp means slower motion: magnetic strength would
decrease

3)

Higher temp means random motions would
knock atoms out of
alignment:
magnetic strength would average to zero

4)

Magnetism is not related to temper
ature; no change

Q38
)

Which one of the following statements concerning permanent
magnets is false?

1
)

The north pole of a permanent magnet is attracted to a south pole.

2
)

All permanent magnets are surrounded by a magnetic field.

3
)

The direction of a ma
gnetic field is indicated by the north pole of a
compass.

4
)

Magnetic field lines outside a permanent magnet originate

from the
north pole and end on
the south pole.

5
)

When a permanent magnet is cut in half, one piece will be a north pole
and one piece wi
ll be

a south pole.

Q39
)

A permanent bar magnet is broken
in half. The two pieces are interchanged,
keeping their orientations fixed, as shown
below. Do the pieces attract or repel?

1)

Attract

2)

Repel