Which end has electrode and insulator sticking above the shell?

Which end has electrode and insulator sticking above the shell?

• A. Firing end
• B. Incorrect heat ranges
• C. Resistors
• D. Projected end

Answer: (D)

In a spark plug, the part that actually sits in the combustion chamber and creates the spark is the end where the center electrode and the ceramic insulator extend beyond the metal shell. This exposed, protruding portion is designed to reach into the chamber so the spark can jump across the gap to the ground electrode. Because this portion projects beyond the shell, it’s called the projected end. That’s why this end is the correct answer—the electrode and insulator stick above the shell here to form the firing area.

In a spark plug, the part that actually sits in the combustion chamber and creates the spark is the end where the center electrode and the ceramic insulator extend beyond the metal shell. This exposed, protruding portion is designed to reach into the chamber so the spark can jump across the gap to the ground electrode. Because this portion projects beyond the shell, it’s called the projected end. That’s why this end is the correct answer—the electrode and insulator stick above the shell here to form the firing area.