What are resistor combinations?

1 Answer
May 28, 2014

Resistor combinations combine series and parallel paths together in a single circuit.

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This is a fairly simple combination circuit. To solve any combination circuit, simplify it down to a single series circuit. This is usually done most easily starting at the farthest point from the power source.

On this circuit, find the equivalent resistance of R_2 and R_3, as if they were a single resistor connected to the others in series.

1 / R_T = 1 / R_2 + 1 / R_3
1 / R_T = 1 / 30 + 1 / 50
1 / R_T = 8 / 150
Take the reciprocal of each to get R_T out of the denominator:
R_T = 150 / 8
R_T = 18.75 Omega

Now add this to the 20 Omega of R_1 and the 20 Omega of R_2 to get a total resistance on this circuit of 58.75 Omega.

Other circuits may be more complex, and you may have to do this several times - going back and forth between series and parallel - until this is simplified down to a simple series or parallel circuit.

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