Electrical resistance

Resistance is how strongly a part of a circuit holds back the current. Moving electrons keep bumping into the metal's atoms and give them energy, so the wire warms up and less current flows. It is measured in ohms. A wire's resistance is larger the longer and thinner it is, and depends on what it is made of: copper is low, which is why it is used for wiring, while nichrome is high and is used in heaters, kettles and irons. For metal wires at a steady temperature, current = voltage ÷ resistance (Ohm's law), so doubling the voltage doubles the current and doubling the resistance halves it.

Depth 1 · Foundation

You know that resistance, in ohms, is how much a part holds back the current and turns its energy into heat, that it grows with a wire's length and thinness and depends on its material, and can use Ohm's law: current = voltage ÷ resistance.

Depths of understanding

1
Foundation
You know that resistance, in ohms, is how much a part holds back the current and turns its energy into heat, that it grows with a wire's length and thinness and depends on its material, and can use Ohm's law: current = voltage ÷ resistance.
Opens after
Electric currentResistance is what holds back the current.

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