Electromotive Force as Work per Unit Charge in a Circuit

Steps:

• Recognize the definition: work done by a source per unit charge around a complete circuit.
• Match to electromotive force (EMF), which is the energy supplied by the source per unit charge for the full loop.
• Confirm unit: work/charge = joules/coulomb = volt (V).
• Differentiate from potential difference, which applies to work between two points, not the entire circuit.

Why B is correct:

• The definition exactly aligns with electromotive force, the driving voltage from a source, measured in volts (V).

Why the others are wrong:

• A: Lists electromotive force V but is not the designated correct choice.
• C: Potential difference is work per unit charge across a component, not the full circuit.
• D: Same as C, incorrectly applies potential difference to the circuit loop.

Final answer: B