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Lesson 3: Reducing Simple Series-Parallel Combination Circuits

fig05111810.gif (1550 bytes)

Some people can look at this circuit and tell right away that the total resistance is given by:

RT = R1 + R2 || R3
 
But it is also important to master the procedures for reducing the circuit, step-by-step, through a series of equivalent circuits.
   

Example

Suppose you are given this set of values:

R1 = 1.3 MW
R2 = 860 kW
R3 = 1.0 MW

Solution

Plug the given values into the equation and solve for RT:

RT = 1.3 MW + 860 kW || 1.0 MW
RT = 1.3 MW + 462 kW
RT = 1.76 MW
But let's approach the problem in a slightly different way--one that will eventually make it possible for you to solve circuits that are far more complicated. Here is the combination circuit with values assigned to the resistors

fig05111811.gif (1800 bytes)

First combine the parallel resistors, R1 and R2, to form equivalent resistance R2, 3:

fig05111812.gif (1526 bytes)

Then combine the series resistors, R1 and R2, 3, to get the value for equivalent resistance R1, 2, 3:

fig05111813.gif (1372 bytes)

:Any resistor circuit can indeed be portrayed as a single resistor.


Author and content provider: David L.Heiserman
Publisher: SweetHaven Publishing Services

Copyright 2005, 2014 David L. Heiserman
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