Page 40 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Fig 7

Area=A=πr 2
Ρ=(R x a)/l=38.5micro-ohm centimeter
Krichhoff’s laws: Kirchhoff’s laws are used in determine the equivalent resistance of a complex network and the
current flowing in the various conductors.

Kirchhoff’s current law also called Kirchhoff’s first law or Kirchhoff’s point rule or Kirchhoff’s junction rule (or
nodal rule).
“At any node (junction) in an electric circuit the sum of current flowing into a node is equal to the sum of current
flowing out of that node or the algebraic sum of current in a network of conductors meeting at a point is zero”.
ie; ΣI=0
For example;
At node A the current entering= the current leaving

i2+i3=i1+i4
Problem
If the currents exiting from junction “a” are to be of 2 amps each, what is the value for the current entering the
junction?
Recall the junction rule for this case ; I =I +I
I
3
2
We know the following values:
I =I =2 amps
2
3
Then, we can solve for current entering the junction I =2+2=4amps
1
Applicable only for junctions in a network.

Fig 8

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CITS : Power - Electrician & Wireman - Lesson 5 - 12