Updated: Dec 9, 2025 | Source: 2023-2027 Question Pool | Topic: G6A
G6A10G6A

Which element of a vacuum tube regulates the flow of electrons between cathode and plate?

Deep Dive: G6A10

The correct answer is A: Control grid. The element of a vacuum tube that regulates the flow of electrons between cathode and plate is the control grid. The control grid's voltage controls electron flow, allowing signal amplification. For amateur radio operators, this is how vacuum tubes work. Understanding this helps when using tube amplifiers.

Why Other Answers Are Wrong

Option B (Suppressor grid): Incorrect. Suppressor grid suppresses secondary emission, it doesn't regulate main electron flow. Control grid is the primary control element. Option C (Screen grid): Incorrect. Screen grid reduces grid-to-plate capacitance, it doesn't regulate electron flow. Control grid is the primary control element. Option D (Trigger electrode): Incorrect. Trigger electrode isn't a standard vacuum tube element - that's more like a thyratron. Control grid is the standard control element.

Exam Tip

Regulates electron flow in tube = control grid. Think 'C'ontrol 'G'rid = 'C'ontrols 'G'rid voltage controls flow. Control grid's voltage regulates electron flow between cathode and plate. Not suppressor grid, not screen grid, not trigger electrode - just control grid.

Memory Aid

Regulates electron flow in tube = control grid. Think 'C'ontrol 'G'rid = 'C'ontrols 'G'rid. Control grid's voltage regulates electron flow between cathode and plate. Primary control element in vacuum tubes.

Real-World Example

A vacuum tube amplifier: The control grid receives the input signal. By varying the control grid voltage, you control the electron flow from cathode to plate, amplifying the signal. The control grid is the primary control element - its voltage directly regulates electron flow.

Source & Coverage

Question Pool: 2023-2027 Question Pool

Subelement: G6A

Reference: 2023-2027 Question Pool · G6 - Circuit Components

Key Concepts

Vacuum tube Control grid Electron flow Tube operation

Verified Content

Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G6A topic.