Potential difference as work per unit charge

Steps:

• Recall that potential difference (voltage) measures the energy change for charges moving through a component.
• Identify the standard definition: it equals the work done (energy transferred) divided by the charge.
• Match this to the options: energy per unit charge directly fits the formula V = W/Q.
• Eliminate mismatches by checking units and concepts for other choices.

Why A is correct:

• Potential difference is defined as the energy transferred per unit charge, given by the formula V = W/Q, where V is voltage, W is work done, and Q is charge.

Why the others are wrong:

• B confuses it with resistance (V = IR relates voltage to current, not energy per current).
• C misapplies it to electric field strength (energy per charge per distance).
• D describes power (energy per time), not voltage.

Final answer: A