Volt as work per unit charge

Steps:

• Recall that voltage (volt) measures electric potential difference as energy per unit charge.
• Energy is measured in joules (J), the unit of work or energy.
• Charge is measured in coulombs (C).
• Thus, 1 volt = 1 joule per coulomb (J/C), linking joule and coulomb.

Why B is correct:

• The SI definition of the volt is the potential difference when 1 joule of work is done to move 1 coulomb of charge (V = J/C).

Why the others are wrong:

• A: Ampere (current) and ohm (resistance) relate via Ohm's law (V = I × R), but do not define the volt.
• C: Coulomb (charge) and ohm (resistance) have no direct relation to voltage definition.
• D: Coulomb-second equals ampere (current unit), unrelated to volt.

Final answer: B