Why do we need parallel circuits? 04/09/2016 Parallel Circuits · PDF fileKey words...

Parallel CircuitsWhy do we need parallel circuits?

©cgrahamphysics.com 201604/09/2016

Parallel or series?

©cgrahamphysics.com 2016

Starter• Draw a circuit diagram for this circuit

Where do we see “parallel” in every day situations?


Starter• Draw a circuit diagram for this circuit

• Add an ammeter to measure the current through the three lamps


Aim

• Explain the difference between series and parallel circuits

• Describe some of the benefits of parallel circuits

Key words

• Series circuit 직렬회로

• Parallel circuit 병렬회로


Have you ever wondered?

Why do we have series and parallel circuits?

The bigger picture ©cgrahamphysics.com 2016

Spot the difference

• Can you draw thediagram for each?

• What is different?


What is a series circuit?

This is a simple series circuit.

Everything is connected in one loop across the

terminals of the battery.

There are no points where the current can split

or join (these are called junctions).

This circuit has two lamps connected in series.

Circuits are always drawn using straight lines.


A parallel circuit is one that contains a point (a junction)

where the current can split (point A) or join (point B).

What is a parallel circuit?

This means that there is more than one path around the

circuit.

A B


Modelling parallel circuits


Investigate


What happens when bulb X breaks?

• If one bulb ‘blows’, or is taken out of its holder, the other bulbs still light.

• You can switch the bulbs on and off independently.


What happens when you add more bulbs?• Each bulb in a parallel circuit

forms a complete circuit with the cells

• This means two light bulbs light to the same brightness as one

• If you add more bulbs, the brightness of all stays the same


Series and parallel

• A series circuit has one path for the current to take (just one loop).

• A parallel circuit has more than one path for the current to take (two or more loops).

+ -

A

+ -

A

A

+ -

A

A

+ -

A

A


+ -

Series and parallel• Are these circuits series or parallel?

+ - + -

+ -+ -

A

ED

C

B


Fairy lights – a series circuit+ -

If one bulb breaks or is removed the circuit is no

longer complete so all of the bulbs will go out.

+ -

break in the circuit©cgrahamphysics.com 2016

Classroom light – a parallel circuit+ -

If one bulb breaks or is

removed the current can

still take the other paths

so the other bulbs will

stay lit.

+ -


Switches in parallel circuits• In fact the classroom lights have more than one bulb on each path

plus a switch.

• This allows us to turn each path of light on and off independently.

+ -


Plenary1. What happens when we add

bulb Z to the circuit?2. In this circuit, which bulb or

bulbs will light up if you close switches A and C?

3. Which bulb or bulbs will light up if you close switches B and C?

4. Do you think the lights in your house are wired in series or in parallel? Explain your choice.


Key words

• Series circuit – only has one path for the electrons. If you add more bulbs, the light gets dimmer. If one bulb breaks, the hole circuit goes out. The voltage is shared between the bulbs

• Parallel circuit – has different branches for the electrons to travel. If you add more bulbs in parallel, all have the same brightness, because each bulb has full voltage from the battery. If one bulb breaks, the others still work


Why do we need parallel circuits? 04/09/2016 Parallel Circuits · PDF fileKey words...

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