A proton is moving in the positive x-direction as shown in Figure 2 with a speed of 1.25 × 106 m s

−1

. Then, the proton enters the region between the two plates.

The potential difference between the plates is 200 V. The electric potential of the upper

plate is higher than the electric potential of the lower plate. The separation distance

between the plates is 35.0 mm. Determine the direction and the magnitude of the

magnetic field that is required between the plates for the proton to continue traveling

in a straight line in the positive x-direction.