Unit:
Year: 1989 Question#: 28
Question: Sphere A carries a charge of +2 coulombs and an identical sphere B is neutral. If the spheres touch one another and then are separated, the charge on sphere B would be
(1 ) +1C
(2 ) +2C
(3 ) 0C
(4 ) +4C
What is this question really asking?
Explanation by: Jill S
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Answer 1
+1
CORRECT
+1 is the correct answer because the two spheres are going to be both at equilibrium after they have touched. Also you know they have to be the same they repel because like charges repel. To get to the answer of +1 C you have to add the coulombs for both spheres and divide by 2. Sphere A= +2 C Sphere B= 0 C 0+2C=+2C/2= +1 C
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Answer 2
+2C
INCORRECT
+2C is incorrect because that would mean that sphere B would have all of the electrons that sphere A had before they touched. If sphere B had all of the electrons then sphere A would have a charge of 0C. If this was the case then the two spheres would not be at equilibrium and they would not repel either because unlike charges do not repel.
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Answer 3
0C
INCORRECT
0C would not be correct answer because if sphere B had 0C then sphere A would have +2C still. The two sphere would be unlike charges and would not repel. Also the two spheres have to be at equilibrium and if sphere A had +2C and sphere B had 0C then the two spheres would not be at equilibrium. return to top
Answer 4
+4C
INCORRECT
+4C can not be the correct answer because +4 would be a greater amount of coulombs then there were even to start with. The answer of +4C would change the whole problem and the system of electrons.
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What's this question really asking?
How many coulombs will be transferred to sphere B after touching sphere A?
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