Multiple choice

If the length and cross sectional area of a conductor are doubled, its resistance will ____.

  1. increase four times

  2. decrease four times

  3. decrease two times

  4. remain unchanged
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Resistance R = ρL/A where ρ is resistivity, L is length, and A is cross-sectional area. If L and A both double: R_new = ρ(2L)/(2A) = ρL/A = R. The resistance remains unchanged because the increase in length (which would increase resistance) is exactly offset by the increase in area (which decreases resistance).

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