Mr Powell 2011 Index What is the link...... Current & Voltage Models AF1 Mr D Powell Understand more about how current and potential difference behaves.

Mr Powell 2011Index

What is the link.....

Current & Voltage

Models AF1

KS3 SCIENCEMr D Powell

Understand more about how current and potential difference behaves in circuits

Use and evaluate models of circuits

Work as a team in different roles

Assessment Focus 1: Thinking scientificallyThread 1: Using models for and in explanations

Mr Powell 2011Index

Mini Whiteboards... SWithout talking to another or sharing any ideas draw a complete electrical circuit with symbols including...

two bulbs, cell, and a switch to turn it on and off.

Now draw another one with the same components but make it so that one one bulb can be turned off and the other is on all the time.

Mr Powell 2011Index

Measuring Current Flow... T

0.5A 1.0A

1.5A

A chemical cell or battery of cells provides a flow of electricity.

This flow registers on a meter called an ammeter which counts electrons as they flow through the wires.

Can you predict the two other ammeter readings, write it on your board and hold it up....

Mr Powell 2011Index

Measuring Current Flow... T

0.3A

In a series circuit the current is the same everywhere as electrons push around the circuit like water down a pipe.

It all travels at the same speed.

Can you predict the other ammeter readings?

0.3A

0.3A

0.3A

Mr Powell 2011Index

Voltmeters tell us how much “potential” there is in a circuit.

What we mean is the potential for an electron to move.

We call this “potential difference” as it is the difference in electrical potential.

It is the same thing as gravitational potential but for electrons!

If each cell is 1.5V what should the voltmeters read....

Potential Difference T

1.5V 4.5V

Mr Powell 2011Index

What is a Coulomb

Electrons are charged particles and each of them have a very tiny charge or attractiveness of -1.6 x 10-19 C.

If we add a load of them together and think of them as a single “sphere of charge” or ball we get a whole coulomb of charge and can think about defining the ampere or amp 1A = 1C/s

C

1.6 x 10-19 C x 6.25 x 1018 electrons = 1C

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Mr Powell 2011Index

Mini whiteboards...

Without talking to another or sharing any ideas with another person imagine you met an alien and had to explain what an electron was.....

Hold it up when you are finished as quick as you can...

Mr Powell 2011Index

What happens inside circuits...

This is a simple current and voltage model...4V

1A

C CC C

C C

C CC

1J

1J

1J

1J

C1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

1J

As the Coulombs of Charge move they release their energy as heat and light (through the bulb)

C

1J

= 1 Coulomb of charge

= 1 Joule of energy

= 1 Second of time

Mr Powell 2011Index

Activity – Modelling Circuits...Instructions...

Work in a team of 5. Your team will be given some information about an electricity model.

It is your job to study this, make a 3D model or diagram and then explain it to the rest of the class.

Each team has a different model.

At the end you all fill in a grid looking at each model as each team explains to the class.

Group Roles

1. Planner: organise team to complete work in allotted time.2. Presenter: writes some notes to explain model to the class or draws a diagram or table

of items to help.3. Evaluator: watches how team performs and suggests improvements using assessment

grid. Tick any boxes achieved.4. Maker 4&5: lead producing the model

Modelling Electricity

One idea to help us explain electricity is to think of a electricity like gravitational potential energy. When you are up high you have lots of it.

We can even use diagrams to help us to understand what is going on...

transfer to heat energy in resistor

Stored chemical energy

transfer to heat energy

in wires

Circuit Rules Any circuit you can use the idea of the following rules;

Mr Powell 2011Index

Level Descriptions for Assessment Focus 1 – Using models for and in explanations..

Level 3 Make a model to represent something you have seen

Level 4 Describe scientific ideas using scientific terms

Describe scientific ideas using a physical model

Level 5 Explain ideas or events using abstract models

Develop a description that uses abstract ideas or models of more than one step

Suggest solutions to problems using scientific ideas

Level 6Explain logically ideas or events using abstract models in new situations

Say what is good or bad about a model

Select the most appropriate model to explain an idea

Level 7 Develop original models to explain ideas and events

Justify the selection of a model to explain an idea

Use language that is ambitious, clear and relevant to the context

Level 8

Explain events logically linking different ideas or models beyond the level expected in normal science lessons

Explain events explicitly linking different ideas or models

Use criteria to evaluate the appropriateness of a model

Mr Powell 2011Index

Level Descriptions for Assessment Focus 1 – Using models for and in explanations..

Level 3 Represent things in the real world using simple physical models

Level 4 Use simple models to describe scientific ideas

Level 5 Use abstract ideas or models of more than one step when describing processes or phenomena

Level 6 Use abstract ideas or models or multiple factors when explaining processes or phenomena

Level 7 Make explicit connections between abstract ideas and/or models in explaining processes or phenomena

Level 8Describe or explain processes or phenomena, logically and in detail, making use of abstract ideas and models from different areas of science

Possible AnswersDonkey Model Ski Slope Central Heating Lorries & Loads Runners in

Race

What forms the circuit in this model?

Track Ski slope tracks Water Pipes Road Network Running Track

What goes round the circuit? Donkeys Skiers Water Trucks Runners

What represents energy in the circuit?

Bags of Hay Height of slopes Heat Load carried

Energy level of runner

from muscles

Where does the current collect energy?

Barn Ski Lift Boiler / Hot water tank Depot Isotonic

Drinks

Where does it give up energy?

To animals in field

As it loses height Radiators Customer Surroundings

Which model is better & why?

Printed Materials

KS3 SCIENCEMr D Powell

Print one set per group.

Assessment Focus 1: Thinking scientificallyThread 1: Using models for and in explanations

Ski Slope Model....

Skiers represent the electrons moving in

wires current flowing

Speed of skiers is the amount of current

flowing i.e. 1A

Height of mountain is the voltage of the cell or potential

difference

Skiing pathways are like wires

Skiers convert energy as they ski down

mountain like a bulb

Skiers can take different paths to show resistance

Skiers are lifted to top of mountain by ski lift which is like a

cell or battery

Donkey Model....

Donkeys move along the farmyard tracks

(charges)

Gates stop the donkeys

They carry bags of hay (energy) to field and other animals to

eat

When track is wet or muddy Donkey is

slowed down

Donkeys pick up hay from barn (energy)

Donkeys speed is current flow

Trucks Model....

Trucks are like charges moving

Traffic lights stop them

Amount of current is speed of trucks

Trucks deliver goods to customers

(energy)

Trucks pick up energy at their supply depot

(energy)Traffic jams slow

them down (resistance)

Central Heating Model....

Water pipes are the wires

Boiler/ Hot water tank is like the cell

giving energy

Water flow is the charges moving

Radiators give out heat (energy) like

bulbs

Flow of water is the current

Timer is like a switch for on/off

Water

Pump

PipesRadiator

Resistor or Bulb

Cell

Wires

Electric Current

Electrical Circuit Model...

Runners in Race Model....

Runners are the charges moving

Runners recombine to show current at

branches

Runners speed is the flow of current

Runners return to start (cell or battery)

Runners can split at branches in parallel

circuit

Runners lose energy from muscles as they

run (energy)

Can drink isotonic drink to boost energy

Energy lost to surroundings as run

Modelling Current Flow....

Current Flow

+

HalfCurrent Flow

=

=

Current Recombines

Current Splits