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KS4 Electricity – Simple CircuitsPowerPoint Presentation

KS4 Electricity – Simple Circuits

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Presentation Transcript

Circuit symbols

Instead of drawing intricate diagrams of electrical components we use circuit symbols to simplify how circuits are set up.

You will need to learn these, how to draw them, and how to identify them.

Filament lamp

Breaks in circuits

Set up the circuit shown….

NO

…does the bulb light?

Why does the bulb not light?

There is a break in the circuit.

For electricity to flow in a circuit it must be able to flow from one terminal of the cell or battery to the other terminal.

Letting electricity pass

Do all materials let electricity pass?

Which materials will and which materials will not?

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).

CONDUCTOR

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

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

INSULATOR

Which of these bulbs will light? Build the circuits!

Electricity will always take the easiest path.

It is easier to flow through a wire than through the bulb.

So in circuits B and C the electricity does not pass through the bulb.

The cell or battery still loses energy because , electricity is still flowing.

This type of circuit is known as a SHORT CIRCUIT.

A.

B.

x

C.

x

Electron flow

Electricity in wires is a flow of electrons along the wire.

Electrical current

What do we call this flow of electrons?

When we talk about current flowing we say that current flows out of the positive terminal of the cell and back into the negative terminal.

Conventional Current

What do we call this flow?

However, the electrons flow from the negative side of the battery to the positive side. These are the particles which are actually moving through the conductor.

Conventional current and Electron flow

When electrons were discovered, physicists worked out what was really happening.

Negatively charged electrons are repelled out of the negative terminal of the cell. They then travel round the circuit and are attracted back to the positive terminal.

What charge do electrons have?

What do two negative charges do if placed near to each other?

What will a positive and a negative charge do to each other?

Negative

They will repel each other.

They will attract each other.

Conventional current

Conventional current

electrons

In an electric c____, currentis the flow of e_______. The bigger the current, the m___ electrons are flowing around the circuit. The w___ carry the electrons from one terminal around the circuit to the other t______.

ircuit

ore

lectrons

ires

erminal

lamps

Set up the two circuits shown:

A.

BRIGHTER

B.

DIMMER

What do we call circuit B?

What happens if you unscrew a bulb in circuit B?

What happens if you unscrew one bulb in Circuit A?

What do we call circuit A?

The other bulb stays lit.

The other bulb goes out.

Series Circuit

Parallel Circuit

In circuit A the bulbs are the brightest.

In which circuit are the bulbs the brightest?

Measuring current I

In a series circuit the current is the same wherever you measure it.

When measuring current ammeters are always placed in series.

Set up the circuit shown below……

…and then record the current using an ammeter in the places shown below.

The current is the same for each ammeter.

What do you notice about the readings?

A

A

A

Measuring current II

For a parallel circuit, the current that leaves the cell or battery is the same as the current that returns to the cell or battery. The current does not get used up by a circuit, just the energy the electrons are carrying.

A1 = A4

…then record the current at the locations shown.

What do you notice about the readings?

Set up the circuit shown below……

A1

A4

0.8

A2

0.4

A3

0.4

0.8

The sum of the currents in the branches of a parallel circuit is the equal to the current that leaves the cell or battery. A1 = A2 + A3 =A4

oltage

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

The cell, battery or p____ s_____ produces the voltage.

lectrons

attery

ush

ower upply

lamps

Measuring voltage I

For a series circuit, the sum of the voltages for each component is equal to the voltage across the cell or battery.

V1 = V2 + V3

Set up the apparatus as shown……

…then record the voltages at the locations shown.

What do you notice about the readings?

V1

1.5

NB Voltmeters are connected in parallel

0.75

0.75

V2

V3

Measuring voltage II

For a parallel circuit, the voltage across the cell/battery is the same as the voltage across each branch.

V1 = V2 = V3

..measure the voltage at the locations shown.

Set up the apparatus as shown….

What do you notice about your readings?

V1

V2

1.5

V3

1.5

1.5

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