Exam-style question
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If a wire has a resistivity of 2.5 x 10^-8 Ωm, a length of 3 m, and a cross-sectional area of 1 x 10^-6 m², what is its resistance?.
- A.7.5 Ω
- B.0.075 Ω
- C.0.75 Ω
- D.75 Ω
Model answer
What a good answer should say
- 7.5 Ω
Explanation
Why this works
The correct answer is 7.5 Ω. This is correct because it applies the Current electricity idea named in the question, using the required quantities and units rather than mixing current, charge, potential difference, resistance, power, or energy.
The other options are less suitable because they use the wrong electrical quantity, an incompatible unit, or a rule from a different circuit context.
Common mistake
No common mistake is linked to this question yet.