"must both positive"

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slidercrank

Joined Nov 6, 2013
5
Volume I - DC
Chapter 6: DIVIDER CIRCUITS AND KIRCHHOFF'S LAWS
Kirchhoff's Current Law (KCL)

"The negative (-) sign on the value of 5 milliamps tells us that the current is exiting the node, as opposed to the 2 milliamp and 3 milliamp currents, which must both positive (and therefore entering the node)."



Suggested correction:
must both be positive
 

Wendy

Joined Mar 24, 2008
22,547
Summarized in a phrase, Kirchhoff's Current Law reads as such:
"The algebraic sum of all currents entering and exiting a node must equal zero"
That is, if we assign a mathematical sign (polarity) to each current, denoting whether they enter (+) or exit (-) a node, we can add them together to arrive at a total of zero, guaranteed.

Taking our example node (number 3), we can determine the magnitude of the current exiting from the left by setting up a KCL equation with that current as the unknown value:



The negative (-) sign on the value of 5 milliamps tells us that the current is exiting the node, as opposed to the 2 milliamp and 3 milliamp currents, which must both positive (and therefore entering the node). Whether negative or positive denotes current entering or exiting is entirely arbitrary, so long as they are opposite signs for opposite directions and we stay consistent in our notation, KCL will work.
Verified...
 

Dcrunkilton

Joined Jul 31, 2004
422
Verified...
Changed at ibiblio to:

The negative (-) sign on the value of 5 milliamps tells us that the current is <italic>exiting</italic> the node, as opposed to the 2 milliamp and 3 milliamp currents, which must both be positive (and therefore <italic>entering</italic> the node).

Credited to slidercrank in theContributor List at ibiblio.org.

Thanks all for getting the errors out,

Dennis
 
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