Potential difference as work per unit charge

Steps:

• Recall the fundamental definition: potential difference (voltage) is the energy transferred per unit charge moved between two points in an electric field.
• Examine option D: it directly states "work done per unit charge," matching the definition V = W/Q.
• Eliminate A, B, and C as they describe derived relationships, not the core definition.
• Confirm D aligns with the unit of volts (joules per coulomb).

Why D is correct:

• It matches the precise definition from electrostatics: potential difference V equals work W done by the electric field per unit charge Q, given by V = W/Q.

Why the others are wrong:

• A: Defines voltage as power per unit current (V = P/I), a consequence of P = VI, not the definition.
• B: Describes Ohm's law (V = IR), relating voltage to current and resistance, not defining it.
• C: Applies to uniform fields (V = Ed), a specific case, not the general definition.

Final answer: D