The correct way to discharge a capacitor is:

• A. To short the terminals with a conductor.
• B. To connect a power supply briefly across the terminals.
• C. To touch both ends of a 20 kΩ, 5 W resistor across the terminals.
• D. To discharge with a screwdriver in the slot.

Answer: (C)

Discharging a capacitor safely means giving its stored energy a controlled path to dissipate as heat, not a direct short. Placing a resistor across the terminals provides that path and limits the current to a safe level. The 20 kΩ, 5 W resistor is sized to keep the initial current I0 = V/R at a safe value and to handle the power P = V^2/R during discharge. The discharge follows an exponential decay with a time constant tau = R × C, so the voltage fades gradually rather than spiking.

A direct short would produce a large surge of current, which can damage the capacitor, wiring, or components and can cause sparks or injury. Touching the terminals with a conductor or a metal tool can also cause a dangerous arc or shock. Trying to discharge briefly with another power supply is unpredictable and may not safely remove the stored energy.

Using a resistor across the terminals provides a predictable, safe energy release and is the standard practice for discharging capacitors. Afterward, verify the voltage with a high-impedance meter before handling the capacitor.