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). return to top


























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. return to top

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. return to top

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. return to top

What's this question really asking?

How must the total current entering a junction compare to the total current leaving the junction? return to top