Ohm’s Law, Resistance & Resistivity — A/L Physics

How do I practise Ohm’s Law, Resistance & Resistivity?

1 question with a worked solution

1. A uniform metallic wire of resistance R is drawn out mechanically so that its length is doubled while its volume remains constant. What is the new resistance of the wire?
   1. A) R / 2
   2. B) 4R
   3. C) 2R
   4. D) R / 4
   Check my answer

   Correct answer: B) 4R

   Resistance is R = ρ L / A. When volume V = A · L remains constant and length L' = 2L, the cross-sectional area must halve: A' = A / 2. Therefore, the new resistance is R' = ρ L' / A' = ρ (2L) / (A / 2) = 4 (ρ L / A) = 4R.

   Show worked solution

   Step 1: Volume V = A · L = constant => L' = 2L implies A' = A / 2. Step 2: R' = ρ L' / A' = ρ (2L) / (A / 2) = 4 (ρ L / A) = 4R. Answer: 4R.
   Modelled on: the A/L Physics examination pattern

Get this auto-marked

Next in the syllabus

Where does Ohm’s Law, Resistance & Resistivity fit in the syllabus?

Unit 7.2 · Year 2 · Term 1