5 rules for a parallel circuit - louisville electrical jatc · a few rules for a parallel circuit...

A Few Rules for a Parallel Circuit

1. A Parallel Circuit has two or more Paths for current to flow through.

2. Voltage is the same across each component in the circuit.

3. The sum of the currents in each path is equal to the current at the source (IT).

4. If one of the paths is broken, current will continue to flow thru the other paths.

A Few More Rules…

5. There are three formulas for finding total resistance.

6. Total Resistance is always SMALLER than the SMALLEST Resistor (or equivelent Resistor).

7. Adding more resistors will cause the total resistance to DECREASE.

. • A Parallel Circuit has two or more Paths for current to flow through. These paths are called branches.

• Voltage is the same across each component in the circuit

24v

24 v 24 v

* The sum of the currents in each path is equal to the current at the source.

* What goes in SHALL to come out!

Resistance Formula #1R/N (R over N)

NRRt

( Resistor Value)

(Number of Resistors)

When all resistors have the Same Value

Resistance Formula #1

NRRt 15

230 tR

Resistance Formula #2 Product Over Sum

When two resistors have different values

21

21

RR

RRRt

Resistance Formula #2

21

21

RR

RRRt

727.233

90

330

3 x 30Rt

Resistance Formula #3Reciprocal Method

When more than two resistors have different values

321

111

1

RRR

Rt

Put your Calculator to Use

You have a button that looks like this

You have a button that looks like this

X

1

1X

Punch in the Numbers

321

111

1

RRR

Rt

5 OHMS 7 OHMS 2 OHMS

Formula: 5 1/X +

7 1/X +

2 1/X =

1/X

2

1

7

1

5

1

1

tR =

Punch in the Numbers

321

111

1

RRR

Rt

5 OHMS 7 OHMS 2 OHMS

Formula: 5 1/X +

7 1/X +

2 1/X =

1/X

2

1

7

1

5

1

1

tR =

Punch in the Numbers

321

111

1

RRR

Rt

5 OHMS 7 OHMS 2 OHMS

Formula: 5 1/X +

7 1/X +

2 1/X =

1/X

2

1

7

1

5

1

1

tR =

Punch in the Numbers

321

111

1

RRR

Rt

5 OHMS 7 OHMS 2 OHMS

Formula: 5 1/X +

7 1/X +

2 1/X =

1/X

2

1

7

1

5

1

1

tR =

Punch in the Numbers

321

111

1

RRR

Rt

5 OHMS 7 OHMS 2 OHMS

Formula: 5 1/X +

7 1/X +

2 1/X =

1/X

2

1

7

1

5

1

1

tR =

Punch in the Numbers

321

111

1

RRR

Rt

5 OHMS 7 OHMS 2 OHMS

Formula: 5 1/X +

7 1/X +

2 1/X =

1/X

2

1

7

1

5

1

1

tR =

Punch in the Numbers

321

111

1

RRR

Rt

5 OHMS 7 OHMS 2 OHMS

Formula: 5 1/X +

7 1/X +

2 1/X =

1/X

2

1

7

1

5

1

1

tR =

If one of the paths is broken,current will continue to

flow.