Magnetic Field Quiz

An electron is in a uniform magnetic field B that is directed out of the plane of the page, as shown above. When the electron is moving in the plane of the page in the direction indicated by the arrow, the force on the electron is directed

• toward the right

• out of the page

• into the page

• toward the top of the page

• toward the bottom of the page

A particle of charge +Q moving with speed v₀ 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

• bottom of the page and proportional to B

• bottom of the page and proportional to v₀

• top of the page and inversely proportional to v₀

• top of the page and inversely proportional to B

• top of the page and proportional to both B and v₀

An object with charge +q passes to the right of one pole of a magnet and at a particular instant is moving with a velocity v toward the bottom of the page, as shown in the figure above. The force exerted on the object by the magnet at that instant is directed into the page. What is the direction of the force exerted on the magnet by the object?

• Out of the page

• Toward the right

• Toward the top of the page

• No direction; the force is zero.

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?

• It remains on the straight line and passes completely between the magnets.

• It curves upward and strikes the top magnet.

• It curves downward and reverses direction before it enters the space between the magnets.

• It stops and reverses direction, then moves to the left along the same straight line.

A beam of protons moves parallel to the x-axis in the positive x-direction, as shown above, through a region of crossed electric and magnetic fields balanced for zero deflection of the beam. If the magnetic field is pointed in the positive y-direction, in what direction must the electric field be pointed?

• Positive y-direction

• Positive z-direction

• Negative x-direction

• Negative y-direction

• Negative z-direction

In a region of space there is a uniform B field in the plane of the page but no E field. A positively charged particle with velocity v directed into the page is subject to a force F in the plane of the page as shown above. Which of the following vectors best represents the direction of B?

• 
• 
• 
• 
• 

Which of the paths above represents the path of an electron traveling without any loss of energy through a uniform magnetic field directed into the page?

• A

• B

• C

• D

• E

A uniform magnetic field B is parallel to the xy-plane and in the +y-direction, as shown above. A proton p initially moves with velocity v in the xy-plane at an angle θ to the magnetic field and the y-axis. The proton will subsequently follow what kind of path?

• A straight-line path in the direction of v

• A circular path in the xy-plane

• A circular path in the yz-plane

• A helical path with its axis parallel to the y-axis

• A helical path with its axis parallel to the z-axis

A charged particle is projected with its initial velocity parallel to a uniform magnetic field. The resulting path is a

• spiral

• parabolic arc

• circular arc

• straight line parallel to the field

• straight line perpendicular to the field

As shown above, a positively charged particle moves to the right without deflection through a pair of charged plates. Between the plates are a uniform electric field E of magnitude 6.0 N/C and a uniform magnetic field B of magnitude 2.0 T, directed as shown in the figure. The speed of the particle is most nearly

• 0.33 m/s

• 0.66 m/s

• 3.0 m/s

• 12 m/s

• 18 m/s