Unit: Electricity
Year: 1997 Question#: 25
Question: The diagram below shows proton P located at a point A near a positively charged sphere.
If 6.4 x 10 -19 joule of work is required to move the proton from point A to point B, the potential difference between A and B is
(1 ) 6.4 x 10-19 V
(2 ) 4.0 x 10-19 V
(3 ) 6.4 V
(4 ) 4.0 V
What is this question really asking?
Explanation by: Gabrielle
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Answer 1
6.4 x 10-19 V
INCORRECT
To use the formula (V=W/q) correctly you must convert 6.4 x 10-19 joules to electron volts or divide by 1 elementary charge (1.6 X 10-19 Coulombs). return to top
Answer 2
4.0 x 10-19 V
INCORRECT
If you used the formula correctly and divided by 1 elementary charge (1.6 x 10-19C) but left out the 10-19 on the bottom, by accident, you would have gotten 4.0 x 10-19V return to top
Answer 3
6.4V
INCORRECT
If you used the formula incorrectly and just divided by 10-19 instead of 1.6 x 10-19C you would have gotten 6.4V. return to top
Answer 4
4.0 V
CORRECT
The potential difference is V=W/q (V=volts (1 joule/coulomb), W= joules, and q= charge in coulombs). Because the answers are in volts (1joule/coulomb) you must divide 6.4 x 10-19 joules by coulombs. Since we are dealing with elementary charges you must convert to coulombs. One elementary charge = 1.6 x 10-19 C. If you divided 6.4 x 10-19 by 1.6 x 10-19 C you will get 4.0 V. return to top
What's this question really asking?
This question is asking you to figure out how to find the potential difference. To do this you must use the formula V=W/q and realize that your carge must be in units of coulombs. return to top
