How is capacitance defined in terms of charge and voltage?

How is capacitance defined in terms of charge and voltage?

• A. Voltage per unit charge (V/C)
• B. Energy per charge (J/C)
• C. Current per voltage (A/V)
• D. Charge per unit voltage (C/V)

Answer: (D)

Capacitance tells you how much charge a capacitor can store for a given voltage. It is defined as the charge divided by the voltage: C = Q / V. This makes the units coulomb per volt, and the standard SI unit is the farad. The other descriptions don’t fit because: voltage per unit charge would be the reciprocal of capacitance (1/C), not C itself; energy per charge is voltage (J/C equals volts), which isn’t a measure of capacitance; and current per voltage isn’t a fixed ratio for a capacitor since i = C dv/dt, so the relation depends on how quickly the voltage changes.

Capacitance tells you how much charge a capacitor can store for a given voltage. It is defined as the charge divided by the voltage: C = Q / V. This makes the units coulomb per volt, and the standard SI unit is the farad. The other descriptions don’t fit because: voltage per unit charge would be the reciprocal of capacitance (1/C), not C itself; energy per charge is voltage (J/C equals volts), which isn’t a measure of capacitance; and current per voltage isn’t a fixed ratio for a capacitor since i = C dv/dt, so the relation depends on how quickly the voltage changes.