Opposition to current flow, measured in ohms; depends on material, length and area.
Resistance R=ρL/A grows with length and resistivity and falls with cross-sectional area. Metals' resistance rises with temperature; semiconductors' falls. Conductance G=1/R in siemens.
A 100 m copper wire of 1.5 mm² has about 1.1 Ω.
Resistance controls how much current flows for a given voltage and converts electrical energy into heat in most circuits.
Opposition to current flow, measured in ohms; depends on material, length and area.
Resistance controls how much current flows for a given voltage and converts electrical energy into heat in most circuits.
Current has to travel further through the material, so resistance grows with length. A wider wire offers more area and reduces resistance.
Usually yes. Metals rise in resistance as they heat, which is why a lamp filament draws less current when cold.
Typical applications include choosing a heater element of the right resistance for a 230 V supply, estimating the voltage drop along a long cable and selecting a current-limiting resistor for an LED.
Study "Voltage" first (topic 3 of 106 in Electrical Engineering). It covers the groundwork this topic builds on.
Copper ρ≈1.7×10⁻⁸ Ω·m. Temperature coefficient. Resistors dissipate energy as heat.
A 100 m copper wire of 1.5 mm² has about 1.1 Ω.
The next topic is "Ohm's law", which builds directly on this one.
It is classed as Beginner in Electrical Engineering (topic 4 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
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