Transcript Modeling Electricity Main Resource

What is the link.....
Mr Powell 2011
Index
Current &
Voltage
Models AF1
Assessment Focus 1: Thinking scientifically
Thread 1: Using models for and in explanations

Understand more about how
current and potential difference
behaves in circuits

Use and evaluate models of
circuits

Work as a team in different roles
Mr D Powell
Mini Whiteboards...
Without 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 2011
Index
Measuring Current Flow...
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....
0.5A
1.0A
1.5A
Mr Powell 2011
Index
Measuring Current Flow...
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
0.3A
Mr Powell 2011
Index
Potential Difference
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....
4.5V
1.5V
Mr Powell 2011
Index
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
- e
e
e- e-- e-- ee- - e- e- e-e e e- e e
e- e- e-
1.6 x 10-19 C x 6.25 x 1018 electrons = 1C
Mr Powell 2011
Index
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 2011
Index
What happens inside circuits...
This is a simple current and voltage model...
4V
1A
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
1J
C
C
C
C
C
C
1J
C
C
C
C
C
1J
As the Coulombs of Charge move they release their
energy as heat and light (through the bulb)
= 1 Coulomb
of charge
= 1 Joule of
energy
= 1 Second of
time
Mr Powell 2011
Index
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.
2.
3.
4.
Planner: organise team to complete work in allotted time.
Presenter: writes some notes to explain model to the class or draws a diagram or table
of items to help.
Evaluator: watches how team performs and suggests improvements using assessment
grid. Tick any boxes achieved.
Maker 4&5: lead producing the model
Mr Powell 2011
Index
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...
Stored
chemical
energy
transfer to
heat energy
in resistor
transfer to
heat energy
in wires
Circuit Rules
 Any circuit you can use the idea of the following rules;
Level Descriptions for Assessment Focus 1 – Using models for and in explanations..
Level 3
Level 4
Level 5
Level 6
Make a model to represent
something you have seen
Describe scientific ideas using Describe scientific ideas
scientific terms
using a physical model
Develop a description
Explain ideas or events using that uses abstract ideas
abstract models
or models of more than
one step
Explain logically ideas or
Say what is good or bad
events using abstract models
about a model
in new situations
Suggest solutions to
problems using
scientific ideas
Select the most
appropriate model to
explain an idea
Use language that is
Justify the selection of a
ambitious, clear and
model to explain an idea
relevant to the context
Level 7
Develop original models to
explain ideas and events
Level 8
Explain events logically linking
Explain events explicitly Use criteria to evaluate
different ideas or models
linking different ideas or the appropriateness of
beyond the level expected in
models
a model
normal science lessons
Mr Powell 2011
Index
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 8
Describe or explain processes or phenomena, logically and in detail,
making use of abstract ideas and models from different areas of
science
Mr Powell 2011
Index
Possible Answers
Donkey
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
To animals in
field
As it loses
height
Radiators
Customer
Surroundings
Where does it give
up energy?
Which model is
better & why?

Print one set per group.
Printed
Materials
Assessment Focus 1: Thinking scientifically
Thread 1: Using models for and in explanations
Mr D Powell
Ski Slope Model....
Skiers represent the
electrons moving in
wires current flowing
Speed of skiers is the
amount of current
flowing i.e. 1A
Skiing pathways are
like wires
Skiers are lifted to
top of mountain by
ski lift which is like a
cell or battery
Height of mountain
is the voltage of the
cell or potential
difference
Skiers convert energy
as they ski down
mountain like a bulb
Skiers can take
different paths to
show resistance
Donkey Model....
Donkeys move along
the farmyard tracks
(charges)
They carry bags of
hay (energy) to field
and other animals to
eat
Donkeys pick up hay
from barn (energy)
When track is wet or
muddy Donkey is
slowed down
Donkeys speed is
current flow
Gates stop the
donkeys
Trucks Model....
Trucks are like
charges moving
Amount of current is
speed of trucks
Trucks pick up energy
at their supply depot
(energy)
Traffic lights stop
them
Trucks deliver goods
to customers
(energy)
Traffic jams slow
them down
(resistance)
Central Heating Model....
Water pipes are the
wires
Water flow is the
charges moving
Flow of water is the
current
Boiler/ Hot water
tank is like the cell
giving energy
Timer is like a switch
for on/off
Radiators give out
heat (energy) like
bulbs
Electrical Circuit Model...
Resistor or
Bulb
Radiator
Wires
Pipes
Electric
Current
Cell
Pump
Water
Runners in Race Model....
Runners are the
charges moving
Runners speed is the
flow of current
Runners can split at
branches in parallel
circuit
Can drink isotonic
drink to boost energy
Runners recombine
to show current at
branches
Runners return to
start (cell or battery)
Runners lose energy
from muscles as they
run (energy)
Energy lost to
surroundings as run
Modelling Current Flow....
Current
Splits
Current
Flow
Half
Current
Flow
+
=
=
Current
Recombines