5 Steps to a 5 500 AP Physics Questions to Know by Test Day (2012)
Chapter 14. Magnetism
391. An electron is moving perpendicular to a 1.0-T magnetic field. The electron has a velocity of 1 × 107 m/s. What is the magnitude of the force acting on the electron?
(A) 1.6 × 10−13 N
(B) 1.6 × 10−12 N
(C) 1.6 × 10−10 N
(D) 1.6 × 10−9 N
(E) 1.6 × 10−8 N
392. Five electrons are moving at the same velocity with respect to a magnetic field, but they are moving at different angles relative to the direction of the magnetic field. Upon which electron does the magnetic field exert the least force?
(A) 0°
(B) 30°
(C) 45°
(D) 60°
(E) 90°
393. A proton moves at a speed of 5.0 × 106 m/s at an angle of 30° relative to a magnetic field. It experiences a force of 4.8 × 10−13 N. What is the strength of the magnetic field?
(A) 0.4 T
(B) 0.8 T
(C) 1.2 T
(D) 2.4 T
(E) 4.8 T
Questions 394–396 use the following figure:
394. A positive charge moves across a magnetic field (see figure). In which direction will the magnetic field exert a force on the charge?
(A) Right
(B) Left
(C) Up
(D) Down
(E) Out of the paper
395. If the charge in the figure above is 1 μC, its velocity is 5,000 m/s, and the strength of the magnetic field is 10 T, then what is the magnitude of the force?
(A) 0.05 N
(B) 0.5 N
(C) 5 N
(D) 500 N
(E) 50,000 N
396. If the charge moving across a magnetic field in the figure was a negative charge instead of a positive one, which of the following changes would occur?
(A) The magnitude of the force would decrease.
(B) The direction of the magnetic field would reverse.
(C) The magnitude of the force would increase.
(D) The magnetic field would exert a force in the opposite direction.
(E) The strength of the magnetic field would decrease.
397. A positive charge travels in a circle within a uniform magnetic field (see figure). The directions of the arrows show the velocity vectors. What is the direction of the force exerted by the magnetic field upon the charge?
(A) Into the paper
(B) Toward the center of the circle
(C) Away from the center of the circle
(D) Out of the paper
(E) There is no force; all force vectors cancel each other out
Questions 398 and 399 use the following figure:
398. In the figure, a piece of wire that is carrying a current passes through a magnetic field. The direction of the current is coming out of the paper. In what direction will the magnetic field exert a force on the wire?
(A) Right
(B) Left
(C) Up
(D) Down
(E) Out of the paper
399. Using the figure, if the current of the wire is 10 A, the strength of the magnetic field is 10 T, and the length of the wire in the field is 1 cm, what is the magnitude of the force exerted on the wire?
(A) 0.01 N
(B) 0.1 N
(C) 1.0 N
(D) 10 N
(E) 100 N
400. This figure is a schematic drawing of a magnetohydrodynamic propulsion unit. The electrodes create a current of ionized seawater as shown by the arrows between them. The direction of seawater and the magnetic field have been indicated. What will be the direction of thrust created by the unit?
(A) Up
(B) Down
(C) Right
(D) Left
(E) Out of the paper
Questions 401–404 use the following figure:
401. The figure shows a section of a wire carrying an electric current (I) as indicated. In which direction will the magnetic field generated by the current flow?
(A) Opposite the direction of the electric current
(B) Into the paper to the left of the wire and out of the paper to the right of the wire
(C) Down
(D) In the same direction as the electric current
(E) Out of the paper to the left of the wire and into the paper to the right of the wire
402. The Points A through E on the figure represent various distances from the center of the current-carrying wire. Which point experiences the strongest magnetic field?
(A) Point A
(B) Point B
(C) Point C
(D) Point D
(E) Point E
403. If the current in the wire above is 5.0 A and Point C is 5 mm from the center of the wire, what is the magnitude of the magnetic field at this point?
(A) 2 × 10−7 T
(B) 1 × 10−4 T
(C) 2 × 10−4 T
(D) 1 × 10−3 T
(E) 2 × 10−3 T
404. A positive charge of 1.0 μC moves at a velocity of 5 m/s in the same direction of the electric current at the radius of Point C (5 mm). What is the magnitude of the force exerted by the magnetic field on the charge?
(A) 1 × 10−10 N
(B) 1 × 10−9 N
(C) 2 × 10−9 N
(D) 1 × 10−8 N
(E) 1 × 10−6 N
405. [For Physics C Students Only] A solenoid has 100 coils/m of wire carrying a current of 10 A. What is the magnetic field produced by the solenoid?
(A) 1.3 × 10−5 T
(B) 1.3 × 10−4 T
(C) 1.3 × 10−3 T
(D) 1.3 × 10−2 T
(E) 1.3 × 10−1 T
406. A conducting rod (L = 2.0 m) is moved along two conducting rails within a magnetic field (B). The rails are hooked up to a light bulb. The resistances of the rails and the rod are negligible, but the light bulb has a resistance of 100 Ω. The rod is moved at a velocity (v) of 10 m/s in the direction indicated. It induces a current (I) in the circuit as indicated in the figure. The magnetic field has a magnitude of 2.0 T and the direction is indicated in the figure. What is the magnitude of the induced electromagnetic field (EMF; ε)?
(A) 2 V
(B) 10 V
(C) 20V
(D) 40 V
(E) 100 V
407. A magnetic field of 0.5 T passes through an area of 6.3 cm2 that is perpendicular to the field. What is the magnetic flux?
(A) 3.2 × 10−4 Wb
(B) 6.4 × 10−4 Wb
(C) 3.2 × 10−2 Wb
(D) 3.2 × 10−1 Wb
(E) 3.2 × 100 Wb
408. The primary coil on a transformer has 100 loops. The magnetic flux changes by 10 Wb/s. What is the magnitude of the EMF (ε)?
(A) 1.0 V
(B) 10 V
(C) 100 V
(D) 1,000 V
(E) 10,000 V
409. A magnetic field of 1.0 × 10−4 T is experienced at a point located 5 cm from the center of a current-carrying wire. What is the magnitude of the current in the wire?
(A) 0.025 A
(B) 0.25 A
(C) 2.5 A
(D) 25 A
(E) 250 A
410. Two wires are placed side-by-side as shown in the figure. The wires have currents of the same magnitude, but they are in opposite directions (indicated by the arrows). How will these wires interact?
(A) They will attract each other.
(B) They will not affect each other.
(C) They will repel each other.
(D) You can’t answer the question without knowing the length of each wire.
(E) You can’t answer the question without knowing the value of the current in each wire.
411. A magnetic field exerts a force on a 10-cm length of wire carrying 2 A of current. The magnitude of the force is 0.1 N. What is the strength of the magnetic field?
(A) 0.1 T
(B) 0.5 T
(C) 1.0 T
(D) 2.0 T
(E) 5.0 T
412. A magnetic field (B = 1.0 × 1010 T) exerts a force of 1.6 × 10−3 N on a charge moving at 1 × 106 m/s perpendicular to the field. What is the magnitude of the charge?
(A) 1.6 × 10−19 C
(B) 1.6 × 10−15 C
(C) 1.6 × 10−9 C
(D) 1.6 × 10−6 C
(E) 1.6 × 10−3 C
413. [For Physics C Students Only] A torus has 100 wires/cm wrapped completely around it. The radius of the torus is 0.5 m. The current through the wire is 10 A. What is the strength of the magnetic field at a point that is 1.0 mm from the outside edge of the torus?
(A) 0 T
(B) 4 × 10−6 T
(C) 8 × 10−6 T
(D) 4 × 10−5 T
(E) 8 × 10−5 T
Questions 414–416 use the following figure:
414. The magnetic field produced by a current in a section of current-carrying wire is shown in the figure. What is the direction of the current?
(A) Up
(B) Right
(C) Left
(D) Down
(E) Into the paper
415. If the strength of the magnetic field at 1 mm away from center of the wire is 5 × 10−3 T, then what is the magnitude of the current traveling through the wire?
(A) 0.025 A
(B) 0.25 A
(C) 2.5 A
(D) 25 A
(E) 250 A
416. If a 1-μC charge moves opposite the direction of the current at 1 cm away from the center of the wire and the velocity of the charge is 5 m/s, then what is the magnitude and direction of the force exerted on the charge by the wire’s magnetic field?
(A) 2.5 × 10−11 N toward the center of the wire
(B) 2.5 × 10−11 N away from the center of the wire
(C) 2.5 × 10−9 N toward the center of the wire
(D) 2.5 × 10−9 N away from the center of the wire
(E) 2.5 × 10−3 N away from the center of the wire
Questions 417 and 418 use the following figure:
417. A negative charge moves across a magnetic field as shown in the figure. What is the direction of the force exerted upon the charge?
(A) 45°
(B) 90°
(C) 135°
(D) 225°
(E) 315°
418. The magnitude of the charge is −1 μC, and it moves at a velocity of 10 m/s in the direction indicated in the figure. If the strength of the magnetic field is 10 T, then what is the magnitude of the force exerted on the charge?
(A) 1 × 10−5 N
(B) 5 × 10−5 N
(C) 7 × 10−5 N
(D) 1 × 10−4 N
(E) 7 × 10−4 N
419. A conducting rod (L = 2.0 m) is moved along two conducting rails within a magnetic field (B). The rails are hooked up to a light bulb. The resistances of the rails and rod are negligible, but the light bulb has a resistance of 100Ω. The rod is moved at a velocity (v) of 5 m/s in the direction indicated. It induces a current (I) in the circuit as indicated in the figure. The magnetic field has a magnitude of 2.0 T and the direction is indicated in the figure.
(A) What is the magnitude of the induced EMF (ε)?
(B) What is the current flowing through the circuit?
(C) How much power is dissipated by the light bulb?
(D) How much energy is used by the light bulb in 60 s?
420. [For Physics C Students Only] You have a resistor-inductor circuit that is hooked up in series with a 12-V battery and a switch. The value of the resistor is 10 Ω. The switch is closed at t = 0. The graph shows the current versus time.
(A) What is the time constant of the circuit?
(B) What is the value of the inductance?
(C) What is the value of the current after two time constants have elapsed?
(D) What is the voltage drop across the resistor after two time constants have elapsed?