Physics for Scientists and Engineers, 6e

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Physics for Scientists and Engineers, 6e
Chapter 24 Gausss Law
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Suppose the radius of the sphere in Example 24.1
(radius 1.00 m, with a charge of 1.00 µC at its
center) is changed to 0.500 m. What happens to
the flux through the sphere and the magnitude of
the electric field at the surface of the sphere?

1. The flux and field both increase.
2. The flux and field both decrease.
3. The flux increases and the field decreases.
4. The flux decreases and the field increases.
5. The flux remains the same and the field
   increases.
6. The flux decreases and the field remains the
   same.

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The same number of field lines pass through a
sphere of any size. Because points on the surface
of the sphere are closer to the charge, the field
is stronger.
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In a charge-free region of space, a closed
container is placed in an electric field. A
requirement for the total electric flux through
the surface of the container to be zero is that

1. the field must be uniform
2. the container must be symmetric
3. the container must be oriented in a certain way
4. The requirement does not exist the total
   electric flux is zero no matter what.

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All field lines that enter the container also
leave the container so that the total flux is
zero, regardless of the nature of the field or
the container.
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Consider the charge distribution shown in the
figure. The charges contributing to the total
electric flux through surface S are

1. q1 only
2. q4 only
3. q2 and q3
4. all four charges
5. none of the charges

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The charges q1 and q4 are outside the surface and
contribute zero net flux through S.
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Again consider the charge distribution shown in
this figure. The charges contributing to the
total electric field at a chosen point on the
surface S are

1. q1 only
2. q4 only
3. q2 and q3
4. all four charges
5. none of the charges

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We don't need the surfaces to realize that any
given point in space will experience an electric
field due to all local source charges.
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Your little brother likes to rub his feet on
the carpet and then touch you to give you a
shock. While you are trying to escape the shock
treatment, you discover a hollow metal cylinder
in your basement, large enough to climb inside.
In which of the following cases will you not be
shocked?

1. You climb inside the cylinder, making contact
   with the inner surface, and your charged brother
   touches the outer metal surface.
2. Your charged brother is inside touching the inner
   metal surface and you are outside, touching the
   outer metal surface.
3. Both of you are outside the cylinder, touching
   its outer metal surface but not touching each
   other directly.

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Charges added to the metal cylinder by your
brother will reside on the outer surface of the
conducting cylinder. If you are on the inside,
these charges cannot transfer to you from the
inner surface. For this same reason, you are safe
in a metal automobile during a lightning storm.