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PSI AP Physics C – Electromagnetic Induction
Multiple Choice Questions
1. The induced current in the closed loop is largest in which one of these
diagrams?
(A)
(B)
(C)
(E)
(D)
2. A loop of wire is placed in a uniform magnetic field directed into the page as
shown above. The magnitude of the magnetic field increases at a constant
rate. What is the direction of the induced current in the loop?
(A) clockwise (B) counter clockwise (C) clockwise then counter clockwise
(D) counter clockwise then clockwise (E) no current in the loop
3. A loop of wire is placed in a uniform magnetic field directed out of the page
as shown above. The magnitude of the magnetic field decreases at a
constant rate. What is the direction of the induced current in the loop?
(A) clockwise (B) counter clockwise (C) clockwise then counter clockwise
(D) counter clockwise then clockwise (E) no current in the loop
4. A square loop of wire is moved at a constant velocity v through a uniform
magnetic field B directed into the page. What is the direction of the induced
current in the loop as it passes through the magnetic field?
Entering the field
Leaving the field
(A) clockwise
clockwise
(B) counter clockwise
counter clockwise
(C) clockwise
counter clockwise
(D) counter clockwise
clockwise
(E) zero
zero
5. A square loop of wire is moved at a constant velocity v through a uniform
magnetic field B directed into the page. What is the direction of the induced
magnetic force on the loop as it passes through the magnetic field?
Entering the field
Leaving the field
(A) left
right
(B) right
left
(C) right
right
(D) left
left
(E) zero
zero
6. A small ring of wire is placed inside a large loop connected to a battery and a
switch. What is the direction of the induced current in the ring just after the
switch is closed?
(A) clockwise (B) counter clockwise (C) clockwise then counter clockwise
(D) counter clockwise then clockwise (E) no induced current
7. A conducting rod is pulled to the right at a constant velocity v through a
uniform magnetic field B directed into the page. The rod rides on two
parallel conducting rails. What is the direction of the induced current in the
circuit?
(A) clockwise (B) counter clockwise (C) clockwise then counter clockwise
(D) counter clockwise then clockwise (E) no induced current
8. A conducting rod of length L is pulled to the right at a constant velocity v
through a uniform magnetic field B. The rod rides two conducting rails
connected to a resistor R. What is the induced current in the circuit? Ignore
the resistance of the rod and the rails.
(A)
𝐵𝐿𝑣𝑅
(B)
𝐵𝑣𝑅
(C)
𝐿
𝐵𝐿𝑣
(D)
𝑅
𝑣𝐿𝑅
(E)
𝐵
𝐵𝑅𝐿
𝑣
9. A conducting rod of length L is pulled to the right at a constant velocity v
through a uniform magnetic field B. The rod rides two metallic rails
connected to a resistor R. What is the rate of energy dissipation in the
circuit? Ignore the resistance of the rod and the rails.
(A)
𝐵𝐿𝑣𝑅
(B)
𝐵𝑣𝑅
𝐿
(C)
𝐵𝐿𝑣
𝑅
(D)
𝑣2 𝑅2 𝐿
𝐵
(E)
𝐵 2 𝐿2 𝑣 2
𝑅
10. A circular loop of wire is placed in the same plane as a long wire carrying a
steady current I. Which of the following actions will not induce the current
in the loop?
(A) increasing current in the wire
(B) decreasing current in the wire
(C) moving the away from the wire
(D) moving the loop in parallel to the wire
(E) rotating the loop with respect to its diameter
11. A bar magnet with the north pole facing down is dropped above a
conducting ring. As the magnet passes through the ring, what is the
direction of the induced current in the ring?
(A) always clockwise
(B) always counter clockwise
(C) first clockwise then counter clockwise
(D) first counter clockwise then clockwise
(E) no induced current in the ring
12. A bar magnet with the north pole facing down is dropped above a
conducting ring. Which one of the following is true about the magnet’s
acceleration as it passes through the ring?
(A) less than g (B) greater that g (C) equals g (D) twice g (E) zero
13. A conducting rod moves to the right at a constant velocity. The rod crosses
a uniform magnetic field directed out of the page. Which of the following
choices correctly describes the electric polarity of the rod as it moves
through the field?
Top End
Bottom End
(A) positive
positive
(B) negative
negative
(C) positive
negative
(D) negative
positive
(E) zero
zero
14. A square loop of wire with a side s and resistance R is placed in a uniform
magnetic field of magnitude B directed into the page. The field begins to
increase according to the formula B = β +γt, where β and γ are positive
constants. What is the direction and magnitude of the induced current I in
the loop?
(A)
𝑆2𝛾
𝑅
(D)
, clockwise
𝑆2𝛽
𝑅
(B)
𝑆2𝛾
𝑅
, counter clockwise (C)
, counter clockwise (E)
𝑆 2 𝛽𝛾
𝑅
𝑆2𝛽
𝑅
, clockwise
, clockwise
15. A circular loop of wire with radius a is placed in a uniform magnetic field
perpendicular to the plane of the loop. The magnetic field varies with time
1
generating an emf Ɛ = βπ𝑎2 𝑡 2 , where β is a constant. What is the rate of
change of the magnetic field?
1
1
(A) βπ𝑎2 𝑡 2
2
1
(B) β𝑡 2
1
(C) βπ𝑎2 𝑡 2
3
3
(D) βπ𝑎2 𝑡 2
2
2
3
(E) βπ𝑎2 𝑡 2
3
16. A circular loop of wire with radius a is placed in a uniform magnetic field
perpendicular to the plane of the loop. The magnetic field varies with time
1
generating an emf Ɛ = βπ𝑎2 𝑡 2 , where β is a constant. Assuming B (t=0) = 0,
which of the following formulas represents the magnetic field as a function
of time?
1
1
(A) βπ𝑎2 𝑡 2
2
1
(B) β𝑡 2
1
(C) βπ𝑎2 𝑡 2
3
3
(D) βπ𝑎2 𝑡 2
2
2
3
(E) β𝑡 2
3
17.A rectangular loop of wire with dimensions a and b moves with a constant
speed v across a uniform magnetic field B directed out of the page. Which of
the following graphs represents the induced current in the loop as a
function of the position x of the leading edge of the loop?
(A)
(B)
(C)
(E)
(D)
18. A conducting rod moves to the right at a constant velocity. The rod crosses
a uniform magnetic field directed out of the page. Which of the following
graphs represents the induced voltage between the ends of the rod as a
function of time?
(A)
(B)
(C)
(E)
(D)
19. Which of the following equations states: “A changing magnetic field induces
an electric field?”
⃗ ⃗⃗⃗
(A) ∮ 𝐸
𝑑𝑙 = −
⃗ ⃗⃗⃗⃗⃗
(C) ∮ 𝐵
𝑑𝐴 = 0
𝑑𝛷𝐵
𝑑𝑡
⃗ ⃗⃗⃗⃗⃗
(B) ∮ 𝐸
𝑑𝐴 =
⃗ ⃗⃗⃗
(D) ∮ 𝐵
𝑑𝑙 = µ0 𝑖𝑐
𝑄𝑒𝑛𝑐𝑙𝑜𝑠𝑒𝑑
Ɛ0
𝑑𝛷𝐵
⃗ ⃗⃗⃗
(E) ∮ 𝐵
𝑑𝑙 = Ɛ0
𝑑𝑡
20. The magnetic field B at all points within the shaded circle has an initial
magnitude B. The magnetic field is directed into the page and begins
decreasing at a constant rate. What is the shape and direction of the electric
field lines induced in the circular space?
(A) parallel lines directed to the right
(B) parallel lines directed to the left
(C) concentric circles in the clockwise direction
(D) concentric circles in the counter clockwise direction
(E) parallel lines directed into the page
21. A circular loop of wire with an area of 6×10-3 m2 is placed in a uniform
magnetic field perpendicular to the plane of the loop. The magnetic field
decreases at a constant rate from 0.04 T to zero in 12 µs. What is the
induced emf in the loop?
(A) 10 V
(B) 20 V
(C) 40 V
(D) 60 V (E) 80 V
22. A circular loop of wire with an area of 4.0×10-3 m2 is placed in a uniform
magnetic field perpendicular to the plane of the loop. The magnetic field
increases at a constant rate from zero to 0.050 T in 10.0 µs. If the electrical
resistance of the loop is 400.0 Ω, what is the rate at which energy is
dissipated in the loop as the field increases?
(A) 0.4 W
(B) 1.6 W
(C) 3.2 W
(D) 1.2 W
(E) 1.0 W
23. A conducting ring with radius r = 0.10 m is placed in a region of a spatially
uniform magnetic field perpendicular to the plane of the ring. The magnetic
field is directed into the page and is decreasing at a rate of 0.050 T/s. What
is the magnitude of the induced electric field in the ring?
(A) 5×10-3 V/m
(B) 2.5×10-3 V/m
(C) 1.5×10-4 V/m
(D) 1×10-5 V/m
(E) 2×10-2 V/m
24. A conducting ring with a radius r = 0.10 m is placed in a region of a spatially
uniform magnetic field perpendicular to the plane of the ring. The magnetic
field is directed into the page and is decreasing at the rate 0.050 T/s. What is
the magnitude of the induced current in the ring if its resistance is 5.0 Ω?
(B) 5π×10-3 A
(B) 2.5π×10-3 A
(C) π ×10-4 A
(D) π×10-5 A
(E) 2π×10-2 A
25. An electric circuit consists of a charged capacitor C, a resistor R and a
switch S. Initially, the switch is open and all devices are connected in series.
A circular loop of wire is placed in the same plane as the circuit. Which one
of the following is true about the induced current in the loop after the
switch is closed?
(A) it is clockwise and increases
(B) it is counter clockwise and increases
(C) it is clockwise and decreases
(D) it is counter clockwise and decreases
(E) it is clockwise and constant
Answer Key
1. A
2. B
3. B
4. D
5. D
6. B
7. B
8. C
9. E
10.D
11.D
12.A
13.D
14.B
15.B
16.E
17.D
18.E
19.A
20.C
21.B
22.E
23.B
24.C
25.D