Basic Qualification · B-004 Circuit components · B-004-005-007
In a vacuum tube, which electrode emits electrons?
- A Grid
- B Collector
- C Plate
- D Cathode
Correct answer: D — Cathode. From the official ISED question bank, verified word for word.
Why
In a vacuum tube, the cathode is the heated electrode that releases electrons into the empty space, acting as the source of the electron flow. The full explanation — and one for every question — is in Pro.
Practise this section
The parts inside the box: resistors, capacitors, inductors, diodes, transistors, tubes and what each does in a circuit.