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I am sorry if this sounds to be a silly question. Maybe I am having trouble interpreting the expression in english since it is not my first language.

I would like to know what the expression "net current" means.

Example of usage: "KCL states that no net current can flow into a node".

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I would like to know what the expression "net current" means.

It's similar to the notion of "net force". If you consider all the forces acting on an object, the net force is simply the vector sum - it's the resultant force.

Similarly, the "vector" sum of currents (in is positive, out is negative) gives the net current into the node.

(If you reverse the sign convention above, you get the net current out of the node.)

KCL simply says that the net current into (or out of) a node is zero.

As an analogy, think of a bank account. Cash deposits in to the account are positive, cash withdrawals out of the account are negative. The net money in to the account is just the "vector" sum of deposits and withdrawals.

If "KCL" applied to this bank account, the net money in to the account would be zero which means that whatever amount is deposited is also withdrawn.

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    \$\begingroup\$ Thank you very much. This is exactly what I needed to understand. \$\endgroup\$ – Leonel Machava Sep 13 '12 at 16:43
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"Net current" means the sum of all currents, keeping current direction in mind. If there's going 1 mA into a node, and 5 mA out, then the net current is 4 mA out.

KCL says that the sum of all ingoing currents must be the same as the sum of all outgoing currents. Note that this doesn't only apply to nodes, but to any bounded region.

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  • \$\begingroup\$ What does it mean: "No net current can flow out of a node"? \$\endgroup\$ – Leonel Machava Sep 13 '12 at 16:12
  • \$\begingroup\$ @Leonel - That the net current must be zero: total in = total out. \$\endgroup\$ – stevenvh Sep 13 '12 at 16:13
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In this context, "net" means the sum or total of the individual currents flowing into (positive current) and out of (negative current) the node. The sum must be zero, because there's no place for any "extra" current to go.

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"net current" = total current

Current is the rate of flow of electric charge. KCL follows directly from the principle of conservation of electric charge and states that the vector sum of all currents flowing through a node -- i.e., the net current -- vanishes. To calculate this vector sum, simply add the currents flowing in (positive) and out (negative) of the node. The result is always zero. Whatever goes in, comes out.

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