Resistance
How much a component opposes current, measured in ohms. A larger resistance means a smaller current for the same voltage.
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Analogy
A narrow pipe is harder for water to flow through than a wide one.
In practice
A longer or thinner wire has more resistance. Heating a metal wire also raises its resistance.
Practice
Flashcards
- Why does a longer wire have more resistance?Charge has further to travel, so it collides with more atoms.
Questions people ask
What affects the resistance of a wire?
Length, thickness and material all matter. A longer wire has more resistance, because charge has further to go. A thicker wire has less resistance, since there is more room for charge to flow. Copper has lower resistance than iron, which is why it is used for cables.
Why do wires get hot when current flows?
Moving electrons collide with the atoms of the wire and give them energy, so the wire warms up. This is called the heating effect of a current. It is useful in a toaster, but wasteful in power cables, which are made thick to keep resistance low.