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

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

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

Answer: (A)

Capacitors in motor circuits can retain a high-voltage charge after power is removed because they store energy in the electric field between their plates. When the system is powered, they charge up; once power is gone, there may not be a quick path for that stored energy to discharge, so the capacitor can remain charged for some time. This is why capacitors are known to hold voltage and can pose a shock hazard if not discharged properly before servicing. Inductors store energy in a magnetic field, not as a static electric charge. When power is removed, the current decays and the energy is released as a brief back-EMF, but it doesn’t persist as a high-voltage charge once the current has died out. Resistors don’t store energy at all; they convert it to heat and dissipate it. Transformers rely on magnetic energy as well, which dissipates quickly when power is removed, so they don’t hold a high-voltage charge either. So, the device that can retain a high-voltage charge after power is removed is the capacitor.

Capacitors in motor circuits can retain a high-voltage charge after power is removed because they store energy in the electric field between their plates. When the system is powered, they charge up; once power is gone, there may not be a quick path for that stored energy to discharge, so the capacitor can remain charged for some time. This is why capacitors are known to hold voltage and can pose a shock hazard if not discharged properly before servicing.

Inductors store energy in a magnetic field, not as a static electric charge. When power is removed, the current decays and the energy is released as a brief back-EMF, but it doesn’t persist as a high-voltage charge once the current has died out. Resistors don’t store energy at all; they convert it to heat and dissipate it. Transformers rely on magnetic energy as well, which dissipates quickly when power is removed, so they don’t hold a high-voltage charge either.

So, the device that can retain a high-voltage charge after power is removed is the capacitor.