Power and current determine voltage across resistor Steps:

• Current I = charge Q / time t = 0.4 C / 1.0 s = 0.4 A.
• Power P = thermal energy / time = 2.0 J / 2.0 s = 1.0 W.
• Potential difference V = P / I = 1.0 W / 0.4 A = 2.5 V. Why C is correct:
• Ohm's law variant V = P/I directly yields 2.5 V from dissipated power and current. Why the others are wrong:
• A: 0.20 V from halving current incorrectly.
• B: 0.40 V confuses current magnitude with voltage.
• D: 5 V from wrongly using 1.0 s for energy dissipation time.

Final answer: C