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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