Answer: 4R.
- A half
- B 2R
- C 4R
- D unchanged
Correct answer: C. 4R
Explanation: R ∝ L²/V at constant volume, so doubling L gives 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.