Download AP Physics Test – Magnetism and EM Induction Name: Each of the

AP Physics Test – Magnetism and EM Induction
Name:
Each of the following 20 multiple-choice questions is worth 3 points, for a total of 60 points on this section.
1) An electron is moving to the right in a region where 4) In which direction will the wires shown in the
diagram above feel a force?
a uniform magnetic field is directed out of the
paper. The direction of the magnetic force exerted
#1
#2
on the electron is
(A) left
left
(B) left
right
(A) upward (B) downward (C) left (D) right
(C) right
left
(E) into the page (F) out of the page (G) Zero force
(D) right right
(E) No force is felt by either wire
2) A wire carries electric current out of the page as
shown in the figure above. If it is within a magnetic
field directed to the left, the magnetic force exerted
on the wire will be directed
5) Two wires carrying equal currents are perpendicular
to each other as shown in the figure. The largest
(A) upward (B) downward (C) left (D) right
magnitude of magnetic field pointing out of the
(E) into the page (F) out of the page
page can be found in region
(A) A (B) B (C) C (D) D (E) None of them
3) A rectangular loop carrying current I is positioned
in a uniform magnetic field as shown in the figures
above. Referring to figure (b) where the loop is
shown from the side, the loop will
(A) move downward (B) move upward (C) remain still
6) A positive charge q is moving with a velocity v
perpendicular to a magnetic field B, as shown
above. If you wanted the particle to move
undeflected through the field, what are the
magnitude and direction of the electric field that
must exist in this region?
(D) rotate clockwise (E) rotate counterclockwise
Magnitude Direction
(A) qvB
Left
(B) B/v
Left
(C) Bv
Right
(D) Bv
Down
(E) Bv
Out of paper
11) A magnetic field of 0.1 T forces a proton beam of
current 1.5 mA to move in a circle of radius 0.1 m.
The plane of the circle is perpendicular to the
magnetic field. Of the following, which is the best
estimate of the work done by the magnetic field on
the protons during one complete orbit of the circle?
7) A rectangular loop of dimensions 0.04 m by 0.06 m
is at rest in a uniform magnetic field of magnitude
0.5 T. The plane of the loop is at a 60º angle to the
field, as shown above from two different angles.
The magnetic flux through the loop is
(A) 0 J (B) 10-22 J (C) 10-5 J (D) 102 J (E) 1020 J
(A) 0 Tm2 (B) 0.6  10-3 Tm2 (C) 1.0  10-3 Tm2
(D) 1.2  10-3 Tm2 (D) 2.4  10-3 Tm2
Questions 8-9 refer to the scenario below, which shows
a flexible, conducting loop of wire placed in a B field
with the plane of the loop perpendicular to the field.
12) A wire of constant length is moving in a constant
magnetic field, as shown above. The wire and the
velocity vector are perpendicular to each other and
are both perpendicular to the field. Which of the
following graphs best represents the potential
difference E between the ends of the wire as a
function of velocity?
8) Which of the following will NOT induce an electric
current in the loop?
(A) increase the magnitude of the field
(B) crush the loop, decreasing its area
(C) move the loop parallel to the field
(D) remove the loop from the field
(E) rotate the loop 45° about a diameter
9) If the magnetic field is decreasing with time, which
way will the induced current flow within the loop?
(A) clockwise (B) counterclockwise (C) into the page
(D) out of the page (E) No current will flow
13) A uniform magnetic field B that is perpendicular to
the plane of the page passes through two loops of
wire, as shown above. The loops are made of
identical wire. The field is confined to a region of
radius a, where a < b, and is changing at a constant
rate. The induced current in the wire loop of radius b
is I. What is the induced current in the loop of radius
2b?
10) A rectangular loop of wire is moving toward a long
current-carrying wire as shown above. In which
direction will the induced current in the loop flow?
(A) I/4
(B) I/2
(C) I
(D) 2I
(E) 4I
14) Two parallel wires, each carrying a current I, repel
each other with a force F. If both currents are
(A) clockwise (B) counterclockwise (C) into the page
doubled, the force of repulsion is
(D) out of the page (E) No current will flow
(A) 2F (B) 2 2 F (C) 4F (D) 4 2 F (E) 8F
Question 18-19 refer to the scenario shown below.
A conducting bar of mass m and length L slides
vertically downward along frictionless rails
connected by a resistor of resistance R. A uniform
magnetic field B is directed into the page, as shown.
15) A coil of wire with 5 turns is shown from a sideview above. It has a radius of 0.2 m, and is in a 0.8
T magnetic field. The loop is rotated by 90° in 2
seconds along the dotted line shown. The total
resistance of the wire is 3Ω. What is the average
emf induced in the coil during this time?
(A) 0.05 V (B) 0.1 V (C) 0.25 V (D) 0.5 V (E) 1 V
16) Two long, parallel wires are separated by a distance
d, as shown above. One wire carries a steady
current I into the plane of the page while the other
wire carries a steady current I out of the page. At
what points in the plane of the page and outside the
wires, besides points at infinity, is the magnetic
field due to the currents zero?
(A) Only at point P
(B) At all points on the line SS'
(C) At all points on the line connecting the two wires
(D) At all points on a circle of radius 2d centered on
point P
(E) At no points
17) In the scenario above, a positively charged particle
is in motion near a current-carrying wire. At the
instant shown, the wire and the particle are both in
the plane of the page, and the particle is moving
into the page. At this instant, what is the direction
of the magnetic force exerted on the particle?
(A) upward
(B) downward
(C) left
(E) into the page (F) out of the page
(D) right
(G) Zero force
18) When the rail has reached terminal speed vt, the
current through the resistor is
(A)
mg
mgB
mgL
gB
(B)
(C) mgBL (D)
(E)
BL
L
B
L
19) When the rail has reached terminal speed vt, the
power output of the resistor is
(A) BLvt
(B)
BLvt
R
B 2 L2 vt2
(D)
R
(C)
B 2 L2 vt
R
B 2 Lvt
(E)
R
20) A bar magnet moves at constant speed all the
way into, through, and out of a circular
conducting loop, shown above. Viewed from
the left, the current flow in the loop will be
(A) clockwise only
(B) counterclockwise only
(C) clockwise, then counterclockwise
(D) counterclockwise, then clockwise
(E) No current will flow
The following free-response questions are each worth 20 points, for a total of 40 points on this section.
21) The plastic cart shown in the figure above has mass 2.5 kg and moves with negligible friction on a
horizontal surface. Attached to the cart is a rigid rectangular loop of wire that is 0.10 m by 0.20 m,
has total resistance 4 , and has a mass that is negligible compared to the mass of the cart. The plane
of the rectangular loop is parallel to the plane of the page. A uniform magnetic field of 2.0 T,
directed into the plane of the page, starts at x = 0, as shown above.
a) On the figure below, show the direction of the induced current in the loop when its front is at 0.12 m.
(5 pts)
Justify your answer.
b) When the front edge of the rectangular loop is at 0.12 m, its speed is 3.0 m/s. At that instant,
calculate the following.
i. The magnitude of the induced current in the rectangular loop of wire. (5 pts)
ii. The magnitude and direction of the net force exerted on the loop of wire. (5 pts)
c) At a later time, the cart and the loop are completely inside the magnetic field, moving to the right at
3.0 m/s. Determine the magnitude of the net force exerted on the loop at that time. (5 pts)
22) A particle with unknown mass and charge moves with constant speed v = 1.9  106 m/s as it passes
undeflected through a pair of parallel plates, as shown above. The plates are separated by a distance
d = 6.0  10-3 m, and a constant potential difference V is maintained between them. A uniform
magnetic field of magnitude B = 0.20 T directed into the page exists both between the plates and in a
region to the right of them as shown. 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 = 0.10 m.
(a) What is the sign of the charge of the particle? Check the appropriate space below. (5 pts)
____ Positive
____ Negative ____ Neutral
____ It cannot be determined from this information
Justify your answer.
(b) On the diagram above, clearly indicate the direction of the electric field between the plates. (3 pts)
(c) Determine the magnitude of the potential difference V between the plates. (5 pts)
(d) Determine the ratio of the charge to the mass (q/m) of the particle. (4 pts)
(e) If the particle were initially traveling slower than 1.9  106 m/s, what would happen to it?
Explain your answer. (3 pts)