A thin wire resists the current more than a thick one, and a long wire more than a short one. In this course we find what decides the resistance of a wire, and we join resistors in series and in parallel. We also see why the lights of a house are always joined in parallel.
3 lessons, about 1 h 15 min3 simulations13 problems6 practice questionsPython in every lesson
Created by StemPy LabThe resistance of a wire is proportional to its length, inversely proportional to its area of cross-section, and it depends on the material and the temperature: . The constant ρ is the resistivity of the material, in ohm metre. Metals have low resistivity, alloys have higher values, and insulators have very high values.
When resistors are joined end to end, one after another, they are in series. The same current passes through each one, the potential differences add up, and the combined resistance is . It is larger than the largest resistor.
When resistors are joined between the same two points, each on its own branch, they are in parallel. The potential difference is the same across each one, the currents in the branches add up, and the combined resistance is given by . It is smaller than the smallest resistor. The lights of a house are in parallel.
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