Simple DC Circuits
and 'Ohm's Law'
The following topics serve as standalone lessons. You can attempt them at your own pace but each presentation is intended as a one-hour lesson.
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Learning aims
Learning aims
To begin to describe how electricity behaves and can be harnessed by understanding its 'properties'.
To understand the relationship between voltage, current and resistance (known as 'Ohm's Law').
(Why am I doing this?)
(Why am I doing this?)
So that I can begin to make predictions about how electrical circuits function.
So in future, I may be able to fix, repair or even design my own simple circuits.
Lesson vocabulary
Lesson vocabulary
Voltage
Voltage
noun: voltage; plural noun: voltages
an electro-motive force (EMF), or potential difference, expressed as volts. It can be thought of as an 'electrical pressure' which causes electrons to be pushed around a circuit.
by Ohm's law, voltage (measured in volts) is equal to the current multiplied by the resistance.
Current
Current
noun: current; plural noun: currents
a flow of electricity which results as a result of the orderly movement of electrons around an electrical circuit. Current is the result of a voltage (potential difference or EMF). When there is no voltage, there can be no current.
by Ohm's law, current (measured in amperes or amps) is equal to the voltage divided by the resistance.
Resistance
Resistance
noun: resistance; plural noun: resistances
the magnitude (amount) of which a substance or device opposes the passage of an electric current, causing energy dissipation.
by Ohm's law, resistance (measured in ohms) is equal to the voltage divided by the current.
Learning Activities
Understanding 'Ohm's Law'
Learning Activities
Understanding 'Ohm's Law'
We cannot see electricity, so to understand 'Ohm's Law' it is sometimes necessary to use analogies.
An analogy is a way of visualising a complicated idea using terms which we are more familiar with but are not necessarily the same.
You could say "it's a bit like... (insert idea here)".
It is important to realise that analogies do not accurately describe what is really going on. They only help make it easier for us to understand.
Electronic Circuit Simulator
Electronic Circuit Simulator
You will use this simulator to build simple DC circuits, which will help build your understanding of how electricity behaves and how understanding Ohm's Law helps us control the current flow in the circuit to make it 'work for us'. Click here to view FULL SCREEN
You will need to take screenshots periodically. To do this, press 'PRINT SCREEN' and then 'CTRL + V' to paste the image into your work.
Reinforcing my learning
Calculating 'Ohm's Law'
Reinforcing my learning
Calculating 'Ohm's Law'
Consider the Ohm's Law triangle below. To use it, we 'cover up' the thing we want to find. What is left behind represents the formula we must use to calculate it.
Lesson 3 - Task list
Lesson 3 - Task list
If you're feeling confident, have a go at answering the questions on the 'calculations sheet' below. Remember to make a copy (and edit that).
If you are less confident and would rather have some additional support, have a go at this calculation sheet instead.
I don't mind which version of the worksheet you attempt, as long as you attempt all four questions.
When finished, attach it to the Google Classroom for feedback.
Lesson 4 - Task list
Lesson 4 - Task list
Make a copy of the 'what I learned today' template.
Using at least 66 words (or a maximum of 72), summarise the Ohm's Law relationship. between voltage, current and resistance.
When finished, attach it to the Google Classroom for feedback.
Ohm's Law
Ohm's Law
Watch how the properties interact with each other by clicking the sliders in the simulator below. You can see that changing one value affects another - but how? What's going on?
The graphic below is a nice way of showing that resistance is inversely proportional to the cross-sectional area of the wire (imagine the circular area if you chopped a piece off).
It is also affected by the length of the wire and the 'resistivity' of the material being used.
Resistivity can be thought of as how much of an 'insulator' the material is. A high resistivity material is a poor conductor and vice versa.
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