Unit: Electricity and Magnetism
Year: 1995 Question#: 21
Question: The diagram below shows the arrangement of three charged hollow metal spheres, A,B,C. The arrows indicate the direction of the electric forces acting between the spheres. At least two of the spheres are positively charged. Which sphere if any could be negatively charged?
(1 ) Sphere A
(2 ) Sphere B
(3 ) Sphere C
(4 ) no Sphere
What is this question really asking?
Explanation by: Chad H
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Answer 1
sphere A
correct
At least two are positive according to the problem. This tells you that two spheres are replusive toward each other. Sphere A is the only sphere that is attracted to the other spheres. Thus this is the negative charged sphere. return to top
Answer 2
sphere B
Incorrect It is replusive toward c return to top
Answer 3
sphere C
Incorrect
It is replusive toward b return to top
Answer 4
no sphere
Incorrect
It can't be no sphere because a is attracting toward b and c, so it has to be negative. return to top
What's this question really asking?
By seeing the electric force between the spheres, what sphere is negative, if any? return to top
