(8c23p20) The electric field just above the surface of the charged drum of a pho
ID: 1869988 • Letter: #
Question
(8c23p20) The electric field just above the surface of the charged drum of a photocopying machine has a magnitude E of 3.20x105 N/C. What is the surface charge density of the drum, assuming that the drum is a conductor? Submit Answer Tries 0/10 (c24p16) (a) The drum of the photocopying machine in the problem above has a length of 46 cm and a diameter of 11 cm. What is the total charge on the drum? Submit Answer Tries 0/10 The manufacturer wishes to produce a desktop version of the machine. This requires reducing the size of the drum to a length of 31 cm and a diameter of 7 cm. The electric field at the drum surface must remain unchanged. What must be the charge on this new drum? Submit Answer Tries 0/10Explanation / Answer
Here ,
for a conductor , electric field just above it is
electric field = sigma/epsilon0
3.2 *10^5 = sigma/(8.854 *10^-12)
sigma = 2.83 *10^-6 C/m^2
the surface charge density is 2.83 *10^-6 C/m^2
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total charge on the drum = surface charge density * surface
total charge on the drum = 2.83 *10^-6 * 2pi * (0.11/2) * 0.46
total charge on the drum = 4.5 *10^-7 C
the total charge on the drum is 4.5 *10^-7 C
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for the smaller drum
total charge on the drum = surface charge density * surface
total charge on the drum = 2.83 *10^-6 * 2pi * (0.07/2) * 0.31
total charge on the drum = 1.93 *10^-7 C
the total charge on the drum is 1.93 *10^-7 C
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