To discharge a capacitor safely, which component value is recommended for the discharge resistor?

To discharge a capacitor safely, which component value is recommended for the discharge resistor?

• A. 15k to 20k ohm, 2 to 5 watt
• B. 100 ohm, 1/4 watt
• C. 1 MΩ, 0.5 watt
• D. 50 ohm, 10 watt

Answer: (A)

When you want to discharge a capacitor safely, you provide a controlled path for the stored energy so the voltage falls steadily after the power is removed. A resistor placed across the capacitor acts as that bleed path, letting the capacitor discharge without a sudden, dangerous current spike or a hot, unsafe situation. The value matters because it sets both how fast the capacitor will discharge and how much heat the resistor will have to handle while it’s discharging. A value in the tens of kilo-ohms range (like 15k to 20k ohms) with a resistor rated at a few watts gives a practical balance: the discharge time is short enough to bring the voltage down in seconds to a minute or so (sufficiently safe for handling), but not so small that the resistor would burn or waste excessive power. The wattage rating ensures the resistor can safely absorb the heat during discharge across the voltages you’re likely to encounter. For example, if the capacitor is charged to a modest voltage, a 15k-ohm resistor will draw only a small current, and the power dissipated remains well within a 2–5 watt rating. Choosing a much lower value would dump a lot of current and heat quickly, while a much higher value would leave the capacitor charged for too long.

When you want to discharge a capacitor safely, you provide a controlled path for the stored energy so the voltage falls steadily after the power is removed. A resistor placed across the capacitor acts as that bleed path, letting the capacitor discharge without a sudden, dangerous current spike or a hot, unsafe situation.

The value matters because it sets both how fast the capacitor will discharge and how much heat the resistor will have to handle while it’s discharging. A value in the tens of kilo-ohms range (like 15k to 20k ohms) with a resistor rated at a few watts gives a practical balance: the discharge time is short enough to bring the voltage down in seconds to a minute or so (sufficiently safe for handling), but not so small that the resistor would burn or waste excessive power. The wattage rating ensures the resistor can safely absorb the heat during discharge across the voltages you’re likely to encounter.

For example, if the capacitor is charged to a modest voltage, a 15k-ohm resistor will draw only a small current, and the power dissipated remains well within a 2–5 watt rating. Choosing a much lower value would dump a lot of current and heat quickly, while a much higher value would leave the capacitor charged for too long.