In an Edison screw lampholder, which part should be live?

• A. The threaded part around the base
• B. The outer shell of the socket
• C. The top contact
• D. The bottom part that the bulb touches when screwed in

Answer: (D)

In an Edison screw lampholder, power reaches the bulb through two points: the central bottom contact and the outer threaded shell. The live conductor is connected to the central bottom contact, which touches the bottom of the bulb’s base when you screw it in. The outer threaded shell is connected to neutral, so it is not live. The other parts around the base aren’t the live path in this type of socket. So the part that should be live is the bottom central contact—the piece the bulb touches at its base.