 
Summary: Physics 208 Exam 3 Name_______________________________________________
You are graded on your work, with partial credit. See the last pages of the exam for formula sheets.
Please be clear and wellorganized, so that we can easily follow each step of your work.
1. (a) (15) A metal airplane with a wingspan of 10 m moves through the earth's magnetic
field, whose magnitude we will approximate as 0.5 T. If the airplane has a velocity of 300
km/hour perpendicular to the magnetic field, what is the induced emf across its wing?
(b) (5) Suppose the airplane were made of insulating plastic rather than conducting metal.
Would there still be an induced emf across its wing? Explain in a few words.
2. Two point charges are moving as shown in the figure.
At a given moment in time, the charge of q = +3.00 µC is located on the y axis at
a distance of 0.20 m from the origin, and is moving to the right with a velocity
v = 2.00 !106
m/s.
At the same time, the charge of q' = !2.00 µC is located on the x axis at a distance
of 0.10 m from the origin, and is moving upward with a velocity v = 1.00 !106
m/s.
(a) (6) Determine the magnitude of the magnetic field at the origin due to the first charge q .
(b) (2) What is the direction of this field? [up, down, to left, to right, into paper, out of
paper?]
(c) (6) Determine the magnitude of the magnetic field at the origin due to the second charge
