EXAM 3 May 14, 1997 PHYS 208
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g = 9.8 m/sec^{2} 
Radius of the earth = 6.38 x 10^{6} m 
Mass of the electron = 9.11 x 10^{31} kg.

e = 1.60 x 10^{19} C 
mu_{0}
 = 1 x 10^{7} Henry/m
4 pi

1
 = 9.0 x 10^{9} N m^{2}/C^{2}
4 pi epsilon_{0}

For all problems, place the equations representing the physics
principles you are using in the box on the page. You may use the
general form of the equation or the form you get applying the
principle to the problem at hand. If no diagram is applicable to
a problem, write "none" in the diagram section.
1. (10 points)
(a) Give a good, quick way of remembering the
BiotSavart law for the magnetic field due to a infinitesimal
segment of current.
(b). Name the magneticfield equivalent of Gauss's Law
for electric fields and explain the analogies between the two.
2. (30 points, from homework)
The circuit shown in the figure is called an RC highpass filter
because high input frequencies are transmitted with greater amplitude
than low input frequencies. If the input voltage is
V_{in} = V_{0} cos(omega t),
find the amplitude of the output voltage.
Diagram:
Principles:
3. (30 points) A metal ring of area A is placed in a constant,
uniform field B in such a way that its area vector makes an angle
theta to the lines of B. The loop now rotates about a diameter so
that theta = omega*t. If the resistance of the coil is R, find the
current through the coil as a function of time.
Diagram:
Principles:
4. (30 points)
A very long, straight metal tube has inner radius a and
outer radius b . A current whose density is J = cr flows down
the tube. Find the magnetic field in the empty region inside
r = a and also within the metal, a < r < b .
Diagram:
Principles:
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