Question

How do you calculate the total resistance of a parallel circuit?

Answer 1

Use the resistance formula:

Example:

You have 4 resistors all connected in parallel. R1 and R2 each have a resistance of 4 ohms, R3 and R4 each have a resistance of 8 ohms. What is the total resistance?

`1/"Rp"` = `1/"R1"` + `1/"R2"` + `1/"R3"` + `1/"R4"`

`1/"Rp"` = `1/4` + `1/4` + `1/8` + `1/8`

(Find a common denominator)

`1/"Rp"` = `2/8` + `2/8` + `1/8` + `1/8`

`1/"Rp"` = `6/8`

(Rp is the reciprocal of this)

Rp = `8/6` = 1.33 ohms