I keep getting “Resistance and resistivity” questions wrong in Current Electricity. What's the trap?
confusing resistance (depends on shape) with resistivity (depends only on material and temperature).
The usual trap: confusing resistance (depends on shape) with resistivity (depends only on material and temperature). How to avoid it: a long thin wire resists more than a short thick one of the same material. Go back to the definition — R = ρL/A: resistance grows with length and shrinks with cross-section; resistivity ρ is the material's own property.
Key point
Resistance and resistivity
Common mistake
confusing resistance (depends on shape) with resistivity (depends only on material and temperature).
Memory tip
a long thin wire resists more than a short thick one of the same material.
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