Answer: 25 W.
- A 100 W
- B 50 W
- C 25 W
- D 200 W
Correct answer: C. 25 W
Explanation: R = V<sup>2</sup>/P = 220<sup>2</sup>/100 = 484 ohm. At 110 V: P = V<sup>2</sup>/R = 110<sup>2</sup>/484 = 12100/484 = 25 W.
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.