Answer: 4R.
- A R/2
- B R
- C 2R
- D 4R
Correct answer: D. 4R
Explanation: Stretching doubles length, halves area (volume constant). R = rho x L/A. R<sub>new</sub> = rho x 2L/(A/2) = 4R.
In series, the same current flows through both resistors; in parallel, the current splits between branches and the voltage across each resistor is the same.
Concept context
Ohm's law, resistors, Kirchhoff's laws, Wheatstone bridge, and cells.