volt

Meaning: The volt is the SI unit of electric potential, potential difference and emf. One volt is one joule per coulomb, so voltage is energy per unit charge. A potential difference is what pushes charge around a circuit. Positive charges tend to move toward lower potential, negative charges toward higher potential.

Equation: ΔV = ΔU/q, where ΔV is the potential difference in volts (V = J/C), ΔU is the change in electric potential energy in joules (J), and q is the charge in coulombs (C).

On the MCAT: A charge accelerated through a potential difference gains kinetic energy qΔV, often expressed in electron-volts (1 eV = 1.60 × 10⁻¹⁹ J). In circuits, V = IR, voltage drops across series resistors add up to the source voltage, and parallel branches share the same voltage. Between parallel plates, the field strength is ΔV/d in V/m.

Common confusion: A volt is energy per charge, not energy. A 9 V battery gives 9 J to each coulomb that passes through it, not 9 J to each electron. Voltage is also a difference between two points, so a single point has a meaningful potential only relative to a chosen reference such as ground.