Question 22 QMED04 - Boiler Technician-Watertender

The Correct Answer is A **Why option A (capacitor) is correct:** A capacitor is an electrical device specifically designed to store electrical energy in an electric field between its plates. Even after a circuit has been isolated (disconnected from the power source) and locked out/tagged out, the capacitor retains this stored charge. This residual stored energy can be lethal or cause serious injury if discharged through a person during maintenance or repair work. Therefore, before any work can safely begin, the capacitor must be actively and intentionally discharged (shorted out through an appropriate discharging device or resistor) to eliminate this stored electrical potential. **Why the other options are incorrect:** * **B) choke coil:** A choke coil (inductor) stores energy in a magnetic field only when current is flowing through it. When the circuit is de-energized and isolated, the magnetic field immediately collapses, releasing the stored energy back into the circuit as a momentary voltage spike. It does not retain a dangerous, long-term residual electrical charge that requires a separate discharging procedure like a capacitor. * **C) resistor bank:** A resistor bank is designed to oppose the flow of current and dissipate electrical energy as heat when current is flowing. It does not store significant electrical energy, and therefore, there is no stored energy to discharge after isolation and de-energization. * **D) potential transformer:** A potential transformer (PT) is an instrument used to step down high voltages for metering and relaying. While it is a hazard due to high primary voltage when energized, it is a non-energy-storing device (like a capacitor) that retains a hazardous charge after isolation. Once isolated, the hazard is removed (though procedures must be followed to ensure the secondary winding is handled correctly, it does not require discharging stored electrical energy).