Physics
.1r. Mirro
Date - - - -Electromagnetism Review
i.
If an ionized hydrogen atom (proton) is moving east in a region where the magnetic field is directed south to
north, how the atom will be deflected if at all
a) out of t~~ page
b) into the page
d) south
e) there is no deflection
c) north
2. The figure shows a uniform magnet ic fi eld B directed to the left and a wire
carrying a current I into the page. The magnetic force acting on the wire is
a) toward the top of the page
b) toward the bottom of the page
c) toward the left
c) toward the right
e) zero
3. The diagram shows a straight wire carrying an electric current I into the page .
The wire is between the poles of a permanent magnet. The direction of the
magnetic force B exerted on the wire is
a)
b)
1
c)
<
d)
>
e) into the page
B is directed out of the page. A proton is
moving upward with velocity v in the +y direction through the fi eld The net
force on the proton can be zero by applying an electric fi eld in which direction?
4 As shown, a unifom1 magnetic field
a) +y
b) -y
\:) -x
d) +x
+y
@
@
@
@
@
(~}
@
@
@
@
@
@
@
0
@
@
e) into the page -x -y
5. An electron travels due north through a vacuum in a region of uniform magnet ic fie ld B which is also
directed due north. The electron w ill
a) be unaffected by the field
c) slow down
e) follow a left-handed corkscrew path b) speed up d) fo llow a right-handed corkscrew path @
@
+x
6. As shown, a uniform magnetic field B is directed out of the page as shown. A charged particle moving in
the plane of the page follows a clockwise spiral pattern of decreasing radius
Which explanation is the most reasonable?
a)
b)
c)
d)
e)
the particle is negative and is speeding up
the particle is positive and is slowing down
the particle is positive and is speeding up
the particle is negative and is slowing down
none of the above
B
<~
@
@
<0 )
l~'
(~)
@
(~)
@
@
(2)
@
@
(~J
r::n
@
@
®
@
@
@
@
7. Three centimeters from a long, straight current carrying wire, the magnetic field produced by the current is
measured as 3 x 10-5 T. What is the current I in the wire?
a) 1.5 A
b) 20 A
c) 30 A
d) 4 .5 A
e) 5.0 A
8. A square loop of wire lies in the plane of the page and carries a
current I as shown There is a uniform magnetic field B upward
parallel to the side MK as shown. The loop wiU tend to rotate
a) about PO with KL coming out of the page
B
R
K --
_
II pi L­
- I)
10 JL===J
b) about PO with KL going into the page
c) about RS with MK coming out of the page
d) about RS with MK going into of the page
e) about an axis perpendicular to the page
S
9. A flat, 300-turn coil has a resistance of30
n
The coil covers an area of 00015 m2 in such a way that its
axis is parallel to an external magnetic field . At what rate must the magnetic field change (Bi t) in order to
induce a current of 0.75 A in the coil?
a) 0 .0075 Tis
b) 2.5 Tis
c) 0.0005 Tis
d) 5.0 Tis
e) 15.0 Tis
10. A wire oflength 0.15 m is passed through a magnetic field B with a strength of O.2 T What must be the
velocity of the wire ifan emf of 0.25 V is to be induced?
'I) 8.3 mls
b) 6.7 mls
c) 00075 mls
d) 012 mls
e) 7.6 mls
N
Date
l Physics
Nlr. Mirro
----­
E lectromagnetism Review
1
1. A horizontal conducting bar is free to slide along a pair of vertical bars, as shown The conductor has
length t = 0.5 m and mass m = 4 kg. As it slides vertically downward under the influence of gravity, it
passes through an inward-direct ed, unifonn magnetic field B = 4.0 T The resistance of the entire circuit
IS R = 2 Q.
a. Draw a free-body diagram below for the system and
state the direction of the magnetic force on the rod
when the conducting bar reaches terminal velocity.
BAR
I
I
I
I
I
I
B
Center: of Mass
I
I
.----[--------J
EB
[---------~---
®
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®
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®
®
®
®
®
®
®
®
®
®
®
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®
R
b. Detennine the terminal velocity (v) of the conducting bar.
After some time T, terminal velocity is reached and the induced emf is measured to be 6 volts.
c. Label the diagram with the correct orientation (direction) of the induced conventional
current under these conditions. Justify your answer.
d. Compute the magnitude of the induced current I
'7
12.
--­
An electron moves with constant speed v = 2 x 107 mls as it passes undeflected through a pair of parallel
3
plates, as shown below. The plates are separated by a distance d = 3.0 X 10- m, and a constant potential
ddference (V) is maintained between them. A uniform magneticjleld, of magnitude B = 0. 50 T directed
into the page, exists both between the plates and in a region to the right of them as depicted 1n the diagram
After the particle passes into the region to the right of the plates where only the magnetic field exists, its
trajectory is circular with radius (r)
a. Compute the magnitude of the magnetic force (F B) experienced by the particle. -; - -x-- ~- --;:
Td -x--x--'-x--x--x--x--x--;v
B
I
-L X
------------~---_
X X X X X x,,~
I
I
x
X
XI
IX XIX
k~IX!:--'
"I
xix
X
X
X
X
x
X
X
,
,
I
: x
I
I
I
x,' x
,/
:x¥'x
x
xx
IX
X
X
I
I
X
X
1 _____ _ - - - - - - - - ­
b. Determine the magnitude of the potential d?tference (V) between
the plates.
c. What is the radius (r) of the particles curved path '7
,lhysi cs
f. Mirro
Date - - - -­
Electromagnetism Review
1
1.
A horizontal conducting bar is free to slide along a pair of vertical bars, as shown. The conductor has
lengt h = 0.5 m and mass m = 4 kg. As it slides vertically downward under the int1uence of gravity, it
passes through an INward-directed, uniform magnetic field 8 = 4.0 T. The resistance of the enti re circuit
IS R = 2
e
n.
a. Draw a free-body diagram below for the system and
state the di rection of the magnetic force on the rod
when the conducting bar reaches terminal velocity
~7
,
l~
BAR
/
r;l.c'n'~ M,,, %)
X
~
f
~
B
%.
~
,(
~
X
~ ~ ,~
,
~
~
,~
"
f.!
:x
~
~
i)(
rx
~
~
<X
~
)(
R
b. Determine t he terminal velocify (v) of the conducting bar.
Ij ::=,c,8
9
r/
/,'7
:=
J
pJ/
~
I~)
IA ri d /l1J (3) v) /: 8
l,r
:=
~(/ y"2)
ry) 1-( -1-) 2­
- .­12
After some time T, t rminal velocity is reached and the induced en?! is measured to be 6 volts
c Label the diagram with the correct orienta tion (direction) of the indu ced conventional
current under these conditions. Justify your answer
)
/.; JI1
d. Compute the magnitude of the induced current
/2
r
?
-R
¥
)(?
~
~
~
7
12 An electron moves with constant speed v = 2 X 10 rn/s as it passes undeflected through a pair of
parallel plates, as shown JJD~. The plates are separated by a distance d = 3.0 X 10-3 m, and a constant
potential d~fference (V) is maintained between them . A uniform magneticfield of magnitude B = 0.50 T
After
directed rtJTO t he page exists both between the plates and in a region to the right of them .,
the particle passes into the region to the right of the plates where only the magnetic field exists, its
trajectory is circular with radius (r).
a. Compute the magnitude of the
magnetic force (Fs) experienced
by the particle.
----------------------------------­
T
x x x x x x x x x x x x
d
~-----------~--B
~
/0 ~ J tI~ 5 .../
x
x
x
x
vf3d
0
/ JI/l
/2
(:l //
x\x
X
X
~I
I
x/ x
x
x
x
x
x
1 _______________
'x
x x X x',
c. What is the radius (r) of the particles curved path?
-
x
, ,/
,,:x'"x
E= d~f
/]//,
x
,
:x
;C
1/
x
\
k,x ,,'
xix x x
b. Determine the magnitude of the potential d{fference (V) between the plates. I
x.. . . ~,
x
~
_J-b)
V
x
'x
0:: - (/ '-10:;'7r.,2;< ,.::')(
t!;;,/~ ~A'~~~ -
x
- 11
)(jv
)(..)
- 7
>< /..J~
~. t. ,1'/'- .-t i )(·, r u )
a~;2~~~