Which device can retain a high-voltage charge after power has been removed?

Which device can retain a high-voltage charge after power has been removed?

• A. Capacitors used in motor circuits
• B. Inductors
• C. Transformers
• D. Resistors

Answer: (A)

Capacitors store energy in an electric field between their plates, so they can hold a voltage even after the supply is removed. In motor circuits, start or run capacitors can stay charged for a while because the dielectric and the circuit’s leakage are relatively limited, meaning the high-voltage charge can persist and must be discharged before servicing. This ability to retain a charge is what makes capacitors the device that can hold a high-voltage charge after power is off. Inductors and transformers store energy in magnetic fields, but that energy is not kept as a persistent high voltage once power is removed. When the circuit is opened, the magnetic energy dissipates quickly (or may produce a brief transient), not a stable high-voltage charge. Resistors don’t store energy at all; they convert it to heat and it vanishes promptly as soon as the source is removed.

Capacitors store energy in an electric field between their plates, so they can hold a voltage even after the supply is removed. In motor circuits, start or run capacitors can stay charged for a while because the dielectric and the circuit’s leakage are relatively limited, meaning the high-voltage charge can persist and must be discharged before servicing. This ability to retain a charge is what makes capacitors the device that can hold a high-voltage charge after power is off.

Inductors and transformers store energy in magnetic fields, but that energy is not kept as a persistent high voltage once power is removed. When the circuit is opened, the magnetic energy dissipates quickly (or may produce a brief transient), not a stable high-voltage charge. Resistors don’t store energy at all; they convert it to heat and it vanishes promptly as soon as the source is removed.