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Learning aim
Learning aim
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.
Ohm's Law - Alternative Graphic
Ohm's Law - Alternative Graphic
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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