Physics Review Question
Unit:
Electricity and magnetism
Year:
1992 Question#:
21
Question:
Two identical spheres carry charges of +0.6 coulomb and -0.2 coulomb, respectively.
If these spheres touch, the resulting charge on the first will be
(1
) +0.8 C
(2
) +0.2 C
(3
) -0.3 C
(4
) +0.4 C
What is this question really asking?
Explanation by: Dana H
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Answer 1
+O.8C
Incorrect, It looks like you simply added the two numbers together. There would have
to be a +1.8 C charge on the sphere to get +.8C charge left on the first one.
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Answer 2
+0.8 C
Correct, after adding +0.6C and -0.2C coulombs you'd get +0.4C then dividing by 2
(two spheres) the result is +0.2C on each sphere.
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Answer 3
-0.3C
Incorrect, there would have to be more negatives than positives in order to have a
negative charge on the first sphere.
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Answer 4
+0.4C
Incorrect, the total charge between both the spheres after they touch is +0.4C but
that charge would evenly distribute across both spheres so each should only have
half of the total.
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What's this question really asking?
What is the charge of the first sphere after they touch?
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