© boardworks ltd 2003. drawing circuit diagrams you must have –straight lines –sharp corners...


Drawing circuit diagrams

• You must have– Straight lines– Sharp corners– Use the correct symbols


Circuit symbols

Light bulb


Can you remember….?

Component Symbol

Battery

Wire

Bulb

Buzzer


Which light bulbs will light?

A

B

C

D


A complete circuit

For electricity to flow in a circuit it must be able to flow from one end of the battery to the other end


Electricity does not only flow inside wires!

• Lots of materials let electricity flow through them.

• An electrical conductor allows electricity to flow through it.

• An electrical insulator does not allow electricity to flow through it.


Testing to see if a material is an electrical conductor or an insulator

Set up the circuit shown and place different materials in the gap in the circuit. Record which materials let electricity through (the bulb lights if electricity flows).

What do we call a material that lets electricity flow through it? CONDUCTOR

What do we call a material that does not let electricity flow through it?

INSULATOR


Electron Flow


Electron flowElectricity in wires is a flow of electrons along the wire from the negative end of the battery to the positive end

What do we call this flow of electrons? Electrical current


The v_____ is a measure of how big a push the e_______ are given as they leave the b_____. The bigger the voltage, the bigger the p___.

Voltage

lamps

oltagelectrons

atteryush


The unit of measure for voltage is the volt, symbol V.

V

Measuring voltage

Voltage is measured using an voltmeter. .


In an electric c____, current is the flow of e_______ carrying electrical energy. The bigger the current, the m___ electrons are

flowing around the circuit.

Current

lamps

ircuit

lectronsore


The unit of measure for current is the amp, symbol A.

A

Measuring current

Current is measured using an ammeter.


Set up the two circuits shown:

In which circuit are the bulbs the brightest?In circuit A the bulbs are the brightest.What happens if you unscrew one bulb in Circuit A?The other bulb stays lit.What happens if you unscrew a bulb in circuit B?The other bulb goes out.What do we call circuit A?Parallel CircuitWhat do we call circuit B?Series Circuit

BRIGHTER

DIMMER

A.

B.


A series circuit• All bulbs will glow dimmer!


Old Christmas tree lights

• If one bulb breaks the circuit is broken - all bulbs go out!


A Parallel circuit

• The bulbs all glow brightly!


Example:In new christmas tree lights

• If one bulb is broken the other bulbs can still light


Think

• How do you think lights on a xmas tree are set up?

• What about street lamps?

• Lights in a car?

• Lights in your house – between rooms?


Series circuit – 1 bulbSeries circuit – 1 bulbSeries circuit – 1 bulbSeries circuit – 1 bulb

Series circuit – 1 bulb


Series circuit – 2 bulbsSeries circuit – 2 bulbsSeries circuit – 2 bulbsSeries circuit – 2 bulbs

Series circuit – 2 bulbs


Parallel CircuitParallel CircuitParallel CircuitParallel Circuit

Parallel circuit


Resistance is how much a material tries to stop electricity passing through it!!!

The symbol = R

Measured in Ohms .using an Ohmmeter.

Resistance


Experiment:How are current and voltage related as electricity flows

through resistor?


Ohm’s Law The voltage and the current in a circuit are directly

proportional to each other when resistance and temperature are constant

Cu

rre

nt

/ A

Voltage/ A

xx

xx

x xx

x

The graph of current against voltage is a straight line

The two quantities current and voltage are directly proportional.

Current-voltage graph for a resistor


Resistance

Resistance

Calculating resistance


V

R

x

Ohms law triangle

Whatever you are trying to find cover it up and it will leave you with the calculation that you need.

So if you are trying to find current (I)...

…cover up I…

…which gives the formula…

II =

VR


A bulb has a current of 20 A and a voltage of 100 V

What is the resistance?

R = V I

= 100 V 20 A= 5


The everyday uses of electricity


1. The heating effect of an electric current

• Applications: irons, kettles etc


The magnetic effect of an electrical current

• Application : electric motor.


The chemical effect of an electrical current

• Application: when electricity is passed through water it breaks up into oxygen and hydrogen gas!

•An electrical current can cause chemical reactions to happen!


Hydrogen gas can then be used as a fuel

1. A complete circuit is required for electric current to flow

2. Circuits can be drawn using circuit diagrams with correct symbols

3. Components can be arranged in series or parallel

Simple CircuitsSimple CircuitsSimple CircuitsSimple Circuits

Simple circuits

Circuit SymbolsCircuit SymbolsCircuit SymbolsCircuit Symbols

Circuit symbols

Switches - series circuitSwitches - series circuitSwitches - series circuitSwitches - series circuit

Switches – series circuit

Switches - parallel circuitSwitches - parallel circuitSwitches - parallel circuitSwitches - parallel circuit

Switches - parallel circuit

Drag & Drop CircuitDrag & Drop CircuitDrag & Drop CircuitDrag & Drop Circuit

Drag & Drop circuit


What is this a symbol for?

Bulb Battery

Switch Wire


What is the name of the tiny particles that move through circuits?

Atoms Currants

Electrodes Electrons


What is the name of something that lets electricity pass through?

Conductor Substance

Insulator Controller


What is the name of something that does not let electricity pass through?

Indicator Terminator

Alligator Insulator


What kind of circuit are the bulbs in?

Parallel Series

Serious Parrot


What is the name of the thing shown below?

Very interesting Very stupid

Variable resistor Variable bulb

© boardworks ltd 2003. drawing circuit diagrams you must have –straight lines –sharp corners...

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