Journeyman Electrician Exam (NEC)General Electrical Knowledge and Plan ReadingEasy
A technician is comparing two conductors, one made of copper and the other of aluminum, both with the same cross-sectional area and length. Which statement accurately describes their electrical resistance?
- AThe aluminum conductor will have higher resistance.
- BThe copper conductor will have higher resistance.
- CBoth conductors will have approximately the same resistance.
- DThe aluminum conductor will have lower resistance.
Show answer & explanationAnswer & explanation
Correct answer: A. The aluminum conductor will have higher resistance.
Aluminum has a higher resistivity than copper. Therefore, for the same cross-sectional area and length, an aluminum conductor will have higher electrical resistance compared to a copper conductor.
Why the other options are wrong
- B. Copper has lower resistivity than aluminum, so its resistance would be lower, not higher.
- C. Copper and aluminum have different resistivities, so their resistances will not be the same.
- D. Aluminum has higher resistivity than copper, so its resistance would be higher, not lower.
Conductor Resistivity Comparison
Resistivity is an intrinsic property of a material that quantifies how strongly it resists electrical current. Copper has lower resistivity than aluminum.
- Lower resistivity means better conductivity.
- Copper is a better conductor than aluminum.
- Resistance is directly proportional to resistivity, length, and inversely proportional to cross-sectional area.
Memory trick: CoPPer is a better Conductor than AlumiNum.