Units of Electrical Energy

Steps:

• Energy unit is joule (J), equivalent to volt-ampere-second (V·A·s).
• V has units of volts (V), I has units of amperes (A), R has units of ohms (Ω = V/A), t has units of seconds (s).
• Compute units for each: A is I·t = A·s (coulombs, charge); B is I²·R = A²·(V/A) = A·V (watts, power); C is V·I·t = V·A·s (joules, energy); D is V²/R = V²/(V/A) = V·A (watts, power).
• Only C matches energy units.

Why C is correct:

• Electrical energy E = V·I·t, from power P = V·I multiplied by time t.

Why the others are wrong:

• A: Units of charge (coulombs), not energy.
• B: Units of power (watts), not energy.
• D: Units of power (watts), not energy.

Final answer: C