Physics Review Question
Unit:
electricity
Year:
1990 Question#:
36
Question:
The diagram below shows the current in three of the branches of a direct current electric
circuit. The current in the fourth branch, between junction P and point W must be
(1
) 1 A towards point W
(2
) 1 A towards point p
(3
) 7 A towards point W
(4
) 7 A towards point P
Explanation by: Danielle (partly)
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Answer 1
1 A toward point W
CORRECT
You realized that Kirchoff's law says the total current entering the junction must
be equal to the total current leaving the junction. So if the total current entering
it was 7A (3A + 4A) then the total leaving must be 7A (6A + 1A).
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Answer 2
1A towards point P
INCORRECT
Right amount of current, bad direction.
Keep in mind that Kirchoff's law says the total current entering the junction must
be equal to the total current leaving the junction.
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Answer 3
7 A towards point W
INCORRECT
Keep in mind that Kirchoff's law says the total current entering the junction must
be equal to the total current leaving the junction.
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Answer 4
7A toward p
INCORRECT
Keep in mind that Kirchoff's law says the total current entering the junction must
be equal to the total current leaving the junction.
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What's this question really asking?
How must the total current entering a junction compare to the total current leaving
the junction?
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