University of California, San Diego
Physics 1b - Thermal Physics & Electromagnetism
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Physics 1B - Tutorial #4
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- In 5 minutes, timed by your tutor, make a list of all the phenomena that
you can think of that are electromagnetic in nature. Think carefully about
those phenomena in which the E-M nature is hidden by charge neutrality. The
group with the longest (verified!) list in each tutorial will receive gift
certificates for free coffee drinks at Espresso Roma. Here's a start
- atomic structure
- friction
- ...
- Metal spheres A and B, standing on insulated supports, are initially in
contact with each other. Sphere C, which has a large negative charge is
placed near the other spheres as shown below. While C is nearby, B is moved
to the right so that the two spheres are now separated, then C is removed.
- A & B are now charged. Draw a diagram of the charge distribution on
each sphere with charge sign indicated. Draw in the E-field lines between the
spheres.
- If B is moved toward A, a spark is likely to jump between the spheres
before they come in contact. Explain why. Where did the energy (work) for
this process originate.
- A and B shown below are stars, of equal mass, in a binary star system.
Points 1 - 5 represent small equal test masses. Draw the two forces,
FA &
FB on each point mass, indicating the magnitude of the force by
the length of the vector. Draw the resultant vector at each point with
a different colored pen.
- A and B shown above are spherical charges of equal magnitude but
opposite sign.
Draw the electric fields due to the two charges,
EA &
EB at each point, indicating the magnitude of the field by
the length of the vector. Draw the resultant vector at each point with
a different colored pen.
- Two concentric spherical conducting shells A & B
(RA < RB) are charged with charges +Q and -Q
respectively. Determine the Elictric Field for a) r < RA,
b) RA < r < RB, c) r > rA.
Draw a diagram for the E-fields.

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Gene Smith
Last
modified: Tues., 25 Apr 2000