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Examples: Kirchoff's Current Law

<^< Kirchoff's Current Law | Course Index | Worksheet: Kirchoff's Current Law >^>(:nl:)

>>frame round<< Example 1:

Determine I'_X_' in the diagram shown.

>><<

>>id=example1 class=question margin=10px frame round<< Taking the current flowing into the junction as positive and that flowing away as negative we can obtain the following relationship:

0.2 + I'_X_' = 0.3 + 0.15 A

(in other words, the sum of the current flowing into the junction is equal to the sum of the current flowing away from the junction)

Thus,

I'_X_' = 0.3 + 0.15 - 0.2 = 0.25 A >><<

>>frame round<< Example 2:

Determine the current flowing between A and B and the current I'_X_' in the diagram shown.

>><<

>>id=example2 class=question margin=10px frame round<< First we can find the current flowing by applying Kirchhoff's Current Law at point A:

I'_AB_' = 0.5 - 0.3 = 0.2 A

Next we can find I'_X_' by applying Kirchhoff's Current Law at point B:

I'_AB_' = I'_X_' - 0.1 = 0.2 - 0.1 = 0.1 A >><<

>>frame round<< Example 3:

The diagram shows how the current is distributed in a domestic hi-fi system. Determine the current available from the accessory socket.

>><<

>>id=example3 class=question margin=10px frame round<< At first this might look difficult but it's just another Kirchhoff's Current Law problem! The maximum input current from the power supply is 6 A. We need to find the current taken by the remainder of the system, anything left over is available for powering any accessories that we might wish to use.

Total current demand is thus:

1.5 + 1.5 + 0.8 + 1.6 = 5.4 A

Available for the accessory socket is thus:

6 - 5.4 = 0.6 A (or 600 mA) >><<(:nl:)(:table style="clear:both":)