1) The drawing shows a current-carrying wire lying along the x axis. The current

Question

1) The drawing shows a current-carrying wire lying along the x axis. The current I is 3.0 A and flows to the right. The wire is 0.76 m long and situated in a uniform magnetic field B. The magnetic field points along the +z axis and has a magnitude of 2.0 T. What is the magnitude F and direction of the magnetic force exerted on the current?
F = ________ N on what axis?

http://www.webassign.net/cj8/c21_q_11.gif


2) An electron passes through two rectangular regions that contain uniform magnetic fields, B1 and B2. The field B1 is stronger than the field B2. Each field fills the region completely. How does the speed v1 of the electron in region 1 compare with the speed v2 in region 2?

http://www.webassign.net/cj8/c21_q_7.gif

a) The speed v1 is greater than v2, because B1 is stronger than B2.
b) The speed v1 is less than v2, because the radius of the circular path in region 1 is less than that in region 2.
c) The speed v1 is less than v2, because the electron accelerates as it goes from region 1 to region 2.
d) The speeds are the same in both regions.
e) The speed v1 is less than v2, because B1 is stronger than B2.

Explanation / Answer

The speeds are the same in both regions. Velocity is proportional to magnetic field, however, you must also take the radius into consideration. Region one has a smaller radius and a larger magnetic field, region two has a larger radius and a smaller magnetic field, this balances out to make the velocity equal in both areas.

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