BASIC ELECTRONICS - OD1633 - LESSON 1/TASK 2
Notice that the sum of the ohmic values of the resistors in both circuits
shown in figure 46 on page 77 is equal (30 Ohms), and that the applied
voltage is the same value (50 volts). However, the total current in figure
44, view B, on page 73, (15 amps) is twice the amount in figure 44, view A
(7.5 amps). It is apparent, therefore, that the manner in which resistors
are connected in a circuit, as well as their actual ohmic values, affect the
total current.
The division of current in a parallel network follows a definite pattern.
This pattern is described by Kirchhoff's law which states:
"The algebraic sum of the currents entering and leaving any junction of
conductors is equal to zero."
This law can be stated mathematically as:
Ia + Ib + ...
In = 0
where Ia, Ib, etc., are the currents entering and leaving the junction.
Currents entering the junction are considered to be positive and currents
leaving the junction are considered to be negative. When solving a problem
using Kirchhoff's law, the currents must be placed into the equation with
the proper polarity signs attached.
Example: Solve for the value of 13 in figure 47 on the following page.
Given:
I1 = 10 amps
I2 = 3 amps
I4 = 5 amps
76
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