Combination of Combination of ResistorsResistors

GCSE PhysicsGCSE Physics

single resistor

2 resistors in parallel

2 resistors in series

3 resistors in series

3 resistors in parallel

Increasing resistance

Resistors in Resistors in seriesseries

Resistors in Resistors in parallelparallel

More about resistance...More about resistance...

Rtotal = R1 + R2

R1 x R2

R1 + R2

Rtotal =

R1 R2

R1

R2

Example QuestionsExample Questions

Calculate the resistance of the following Calculate the resistance of the following combination of resistors-combination of resistors-

5 Ωa) 7 ΩRtotal = R1 + R2

= 5 + 7 =12 Ω

12 Ω

4 Ω

b)

R1 x R2

R1 + R2

Rtotal =

= 12 x 4 / (12 + 4)

= 48 / 16 = 3 Ω

6Ω

2Ω7Ωc)

R1 x R2

R1 + R2

Rtotal =

= 6 x 2 / (6 + 2)

= 12 / 8 = 1.5 Ω

Calculate the resistance of the parallel section first…

1.5Ω 7Ω

This now simplifies the combination to this…Rtotal = R1 + R2

= 1.5 + 7

= 8.5 Ω

Pg 131, Q26Pg 131, Q26

g) – j)g) – j)

Practise QuestionsPractise Questions

Pg 131, Q26Pg 131, Q26

Remember the equations-Remember the equations-

Rtotal = R1 + R2

R1 x R2

R1 + R2

Rtotal =

Remember this example question:Remember this example question:

V1

V2

6 V

3 A

A1

A2

V3

A3

What is the easiest path for the Coulombs of Charge?

All bulbs are identical in

power rating