Physics Review Question

Unit: Electricity
Year: 1996 Question#: 31
Question: In a lightning strike, a charge of 18 coulombs is transferred between a cloud and the ground in 2.0 x 10-2 second at a potential difference of 1.5 x 106 volts. What is the average current produced by this strike?

(1 ) 3.6 x 10-1 A
(2 )9.0 x102 A
(3 ) 3.0 x104A
(4 ) 7.5 x107A
What is this question really asking?




Explanation by: Jennifer I
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Answer 1
3.6 x 10-1A
INCORRECT

This is the product of charge and time which does relate to current but is not a familiar equation and does not produce the correct units. return to top























Answer 2
9.0 x 102

CORRECT

Current (I)= charge/ time= 18 coulombs/2.0 x10-2s
= 9.0 x 102 A
Potential Difference is not needed.
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Answer 3
3.0 x 10 4 A
INCORRECT
This is the product of charge and potential difference which does not deal with the time factor. Since current is a measurement of the amount of charge that passes a certain point, it must be restricted by a time limit which must show up inthe calculations.
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Answer 4
7.5 x 10 7 A
INCORRECT
This value can not be achieved using the given data.
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What's this question really asking?

What is the current of a lightning strike with a charge of 18 coulombs which travels for
2.0 x 10-2 seconds and has a potential difference of 1.5 x 10 2 volts?
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