🔍 Key Concepts

• Behavior and properties of vacuum tube filaments • What it means to reactivate or "get emission back" from an old tube • Differences between pure metals vs coated/compound filaments in tubes

💭 Think About

• Which filament material is known for having its electron emission improved again by special heating or operating procedures? • Think about which of these materials is typically used as a base metal that can be rejuvenated, rather than as a stable oxide or compound coating. • Among the choices, which is most commonly associated with power and transmitting tubes that sometimes can be "brought back" after hours of use?

✅ Before You Answer

• Be clear on what reactivated means in tube maintenance: restoring emission from the cathode/filament. • Ask yourself which options are base filament metals and which are oxides or compounds used mainly as coatings. • Eliminate materials that are more likely used as a coating on a cathode rather than the main filament that can be directly rejuvenated.