How to calculate total resistance of a parallel circuit

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Deion Adel
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How to calculate total resistance of a parallel circuit

Post by Deion Adel »

Can anyone help me, please. I've got to find the total resistance of a parallel circuit. There are three given resistors (no given voltage, current, and power, it's only 3 resistors) and the third resistor is initiated into infinite. How can I solve the total resistance when there is an infinite given or value in one of the resistors? I read the Comparisons of Resistor in Series and in Parallels but this problem is not solved.
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Externet
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Re: How to calculate total resistance of a parallel circuit

Post by Externet »

Solve the parallel value of the two resistors that do not initiate in infinity.
When done, solve the resulting values of the new parallel with both values from infinity to whatever that third resistor is.
- Abolish the deciBel ! -
dyarker
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Re: How to calculate total resistance of a parallel circuit

Post by dyarker »

It sort-of is in para 4-2 of your link. But anyway -

Code: Select all

                      1
 Rt = --------------------------
           1         1        1
         ----   +  ----  +  ----
          R1        R2       R3
In words
1 over R1 gives its' conductance
1 over R2 gives its' conductance
1 over R3 gives its' conductance
sum the conductances
1 over conductance total gives parallel resistance total

Can be any number of resistances. (1 or 0 would be silly though! :) )
Or, if all are equal then divide resistance of 1 resistor by the number of resistors.

an infinite resistance is an open, don't include in calculation.

(continued in next post.)

Cheers,
Dale Y
dyarker
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Re: How to calculate total resistance of a parallel circuit

Post by dyarker »

A shorter way to do the above for only 2 resistors is product over sum.
"|" used to mean parallel of the two names resistors
R1|R2 = (R1 * R2) / (R1 + R2)

To parallel R3 later

RT = (R1|R2 * R3) / (R1|R2 + R3)

called to diner, be back

okay, back
Since R for R1 parallel R2 was calculated first, then paralleling R3 with that previous is is two resistances again.

Cheers,
Dale Y
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