Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

What should be used to discharge a capacitor prior to ohmmeter testing?

1. A 10,000 ohm resistor

2. A 20,000 ohm, 2 to 5 watt resistor

3. A 1,000 ohm resistor

4. A 50,000 ohm resistor

The correct answer is: A 20,000 ohm, 2 to 5 watt resistor

Using a resistor to discharge a capacitor prior to ohmmeter testing is crucial for safety and for obtaining accurate readings. The correct choice of a 20,000 ohm, 2 to 5 watt resistor strikes an effective balance between being able to discharge the capacitor quickly while also handling the power without overheating. When discharging a capacitor, it is essential to use a resistor with a high enough resistance to safely reduce the stored voltage without allowing excessive current to flow, which could lead to a dangerous situation or damage to the capacitor or the resistor itself. The 20,000 ohm value is sufficient to limit the current while allowing the capacitor to discharge effectively. The power rating of 2 to 5 watts is also important. Capacitors can store a significant amount of energy, and if the resistor has too low of a power rating, it might overheat and fail during the discharge process. Choosing a resistor within this range will ensure safety and reliability during the discharging process. In contrast, lower resistance values like a 1,000 ohm resistor might allow too much current to pass, leading to quicker discharges but at increased risk of damaging components. Similarly, while a 50,000 ohm resistor would limit the current further, it