AP Physics 2 Magnets
An electron is moving to the right, as shown in the figure above. It passes through the shaded region, which contains a magnetic field. The electron travels along a path that takes it through point P. The gravitational force on the electron is negligible. What is the direction of the magnetic field?
A Into the page
At the instant shown above, an electron is moving to the right along a straight line midway between two identical bar magnets. Which of the following describes the path of the electron as it continues to move?
A It remains on the straight line and passes completely between the magnets.
A small, negatively charged object is moving vertically upward parallel to a wire carrying a downward current, as shown in the figure. Which of the following statements best describes the dominant force or forces exerted by the wire on the object?
A Magnetic forces are the dominant forces.
A long, straight wire in the plane of the page carries a current I toward the right, as shown above. What is the direction of the magnetic field at point P, which is in the plane of the page and above the wire?
A Out of the page
A compass is placed above a current-carrying wire so that the compass needle completely lines up along the magnetic field created by the wire. How will the compass needle be aligned?
A Perpendicular to the wire
The figure shows magnetic field lines surrounding a bar magnet. Which of the following systems will produce field lines most similar to the magnetic field lines of the bar magnet?
A The electric field surrounding a pair of particles with charges of the same magnitude, but one positive and the other negative
Two wires in the same circuit are very close to each other and oriented parallel to one another, with currents traveling in the same direction. Each wire exerts a force on the other wire. Which of the following correctly describes the fundamental cause of these macroscopic forces?
A The moving charges in each wire create magnetic fields that exert forces on the moving charges in the other wire.
Two long parallel wires, separated by a distance d, carry equal currents I toward the top of the page, as shown above. The magnetic field due to the wires at a point halfway between them is
A zero in magnitude
A student is investigating the direction of the force exerted on charged particles by a current-carrying wire. A beam of positively charged particles, one of which is shown above, initially moves to the right with speed v, above and parallel to the wire. The current in the wire is turned on and is directed toward the left. Four labeled detectors are arranged as shown in the diagram and can detect the particles. Which of the detectors is most likely to first detect the particles?
B B
A student has a small disc of unmagnetized iron and places it close to the north pole of a magnet. In the figures below, the arrows represent the alignment of the magnetic fields of domains in the disc. Which of the figures best represents the alignment of the domains before and after the disc is placed near the magnet?
B Before- random directions After- aligned downward
The figure above represents the random orientations of the magnetic dipoles in a block of iron and a block of lead. Iron is ferromagnetic and lead is diamagnetic. The two blocks are placed in a magnetic field that points to the right. Which of the following best represents the orientations of the dipoles when the field is present?
B Iron- aligned right Lead- random directions
Some materials can become strongly magnetized. Which of the following is believed to be the microscopic cause of the macroscopic magnetic field in such materials?
B The fields of the individual electrons due to the property of electron spin.
An object with charge -q is in motion near a wire that has a current I to the right. At the instant shown in the figure above, the object is traveling to the right with speed v. Both the wire and the motion of the object are in the plane of the page. Which of the following statements is true about the force on the object due to the current I at the instant shown?
B The force is directed toward the bottom of the page.
A rectangular circuit that is placed on a horizontal table is represented in the top-view figure above. The circuit consists of a battery with potential difference ΔV0 , an open switch, a resistor of resistance R, and a capacitor of capacitance C that are all connected in series. The switch is closed at t=0 . What is the direction of the magnetic force exerted on the wire on the left side of the circuit due to the wire on the right side of the circuit after the switch is closed and current flows through the circuit?
B To the left
A particle with charge q, mass m, and speed v moves in a circular path of radius r perpendicular to a uniform magnetic field of magnitude B. If a second particle with charge 2q, mass 2m, and speed v was also moving perpendicular to the field, the radius of its circular path would be
B r
A 100-turn wire coil has a resistance of 400 Ω and a cross-sectional area of 0.01 m^2. The coil is placed in a magnetic field directed parallel to the axis of the coil. If the field changes at a rate of -0.4 T/s, what is the current induced in the coil?
C 1 x 10^-3 A
A charged object with a net charge of +10 mC moves perpendicularly to a uniform magnetic field with magnitude 5 T . The force exerted on the object by the magnetic field is 0.5 N. What is the magnitude of the velocity of the object?
C 10 m/s
A positively charged particle is moving horizontally when it enters the uniform electric field between two parallel charged plates, as shown in the figure above. Which of the following could show the x and y positions of the particle as a function of time t ?
C Positive slope from 0 to t Negative concave downward curved slope from 0 to t
A rectangular circuit that is placed on a horizontal table is represented in the top-view figure above. The circuit consists of a battery with potential difference ΔV0 , an open switch, a resistor of resistance R, and a capacitor of capacitance C that are all connected in series. The switch is closed at t=0 .
C The magnetic domains in the iron disk become aligned with the magnetic field created by the wires in the circuit.
The figure above shows a bar magnet with two metal paper clips hanging from it. Which of the following explains why the bottom paper clip is attracted to the top paper clip?
C The top paper clip's magnetic domains are temporarily aligned, making the clip magnetic while it touches the bar magnet.
The gray rectangle in the figure above represents a region of uniform magnetic field directed out of the page. A square loop of wire of side s is in the plane of the page and is pulled at constant speed v through the field. Which of the following could show the current I in the loop as a function of the position of the right edge of the loop?
C [0, s]- above the x-axis [s, 2s]- along the x-axis/zero [2s, 3s]- below the x/axis
A proton is moving at 4.4 x 105 m/s in the plane of the page when it enters a magnetic field of magnitude 0.04 T perpendicular to the page, as shown in the figure above. The radius of curvature of the path of the proton as it moves through the magnetic field is approximately which of the following?
D 1 x 10^-1 m
An electron is located 1.5cm above a wire with current 2.5A, as shown above. The wire exerts a force of 1.3×10^−16N on the electron. What are the magnitude and direction of the velocity of the electron?
D 2.4×10^7ms to the right and parallel to the wire
An electron with speed 3×10^3 m/s is moving in a circle perpendicular to a 0.001 T uniform magnetic field. What is the acceleration of the electron?
D 5.3×10^11 m/s^2
The figure above shows a bar magnet and a conducting wire loop that is fixed in place. Which of the following would cause an induced current in the wire?
D I and III only
The figure above shows two bar magnets of different size and a point X near one end of each magnet. For which magnet is the strength of the magnetic field at point X greater?
D It cannot be determined from the given information.
The figure shows the paths of three particles in a uniform magnetic field. Each particle has the same velocity when it enters the field, and each path is in the plane of the page. One particle has a positive charge, one has a negative charge, and one has no net charge. What is the direction of the magnetic field?
D It cannot be determined without knowing which paths correspond to the positively and negatively charged particles.
The figure above shows a long, straight wire that has a steady current I in the +y-direction. A small object with charge +q hangs from a thread near the wire. A student wants to investigate the magnetic force on the object due to the current but is not able to observe or measure changes in the tension in the string. Of the following actions that the student can take, which will allow the student to observe a reaction of the object due to the magnetic force on it?
D Moving the object in the +y-direction
A metal spring has its ends attached so that it forms a circle. It is placed in a uniform magnetic field, as shown above. Which of the following will NOT cause a current to be induced in the spring?
D Moving the spring parallel to the magnetic field
Each of the figures below shows the path of a charged particle moving in the plane of the page in a magnetic field that is perpendicular to the page. If the mass, speed, and charge of the particles are the same, in which case does the field have the greatest magnitude?
D Sharp curve upward back towards the left/original path
A wire loop is rotated in a uniform magnetic field about an axis perpendicular to the field, as shown above. How many times is the induced current in the loop reversed if the loop makes 3 complete revolutions from the position shown?
D Six
A bar magnet moves toward the center of a loop of wire, as shown above. Which of the following statements correctly describes the magnetic fields from the bar magnet and the loop as the magnet moves toward the loop?
D The bar magnet and the loop both create dipole fields.
A particle of charge +Q moving with speed vo enters a region of constant magnetic field B directed into the page, as shown above. The initial direction and magnitude of the acceleration of the particle as it enters the magnetic field is toward the
E top of the page and proportional to both B and vo
