3 . A parallel plate capacitor produces an electric field perpendicular to the magnetic field, as shown in
the figure. The magnetic field is directed into the page in the –z direction. The magnetic and electric
fields are adjusted so that a particle of charge +1e , moving at a velocity of v will pass straight
through the fields in the +y direction. Which of the following changes will cause the particle to deflect
to the left as it passes through the fields?
(A) Increasing the emf (ε) of the battery
(B) Doubling the charge to +2e
(C) Changing the sign of the charge to –1e
(D) Increasing the velocity of the particle
(E) Decreasing the magnetic field strength
4 . A lab cart with a rectangular loop of metal wire fixed to the top travels along a frictionless
horizontal track, as shown in the figure. While traveling to the right, the cart encounters a region of
space with a strong magnetic field directed into the page. Which of the following graphs best depicts
the velocity of the cart as a function of time as it enters, passes through, and finally exits the magnetic
field on its journey?