Identify the important features of the semiconductor devices from the following:
(A) Semiconductor devices require cathode heating for the production of charge carriers.
(B) They have long life and high reliability.
(C) They are small in size and consume low power.
(D) They operate at high voltage.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B) and (C) only
Semiconductor devices (diodes, transistors, ICs) replaced the vacuum tubes of earlier electronics, and their features are best seen by comparison with a vacuum tube.
(A) Semiconductor devices require cathode heating for the production of charge carriers. — Incorrect. A vacuum tube needs a heated cathode to emit electrons; in a semiconductor the carriers are already present in the solid, so no heated cathode is needed.
(B) They have long life and high reliability. — Correct. There is no filament to burn out, so the life is long.
(C) They are small in size and consume low power. — Correct. No heater is needed, so the power drawn is small and the devices can be made very compact.
(D) They operate at high voltage. — Incorrect. They work at low voltages, of the order of a volt, and do not need the high voltage of a vacuum tube.
NCERT (2026-27):
Classification of Metals, Conductors and Semiconductors – “… Note that the supply and flow of charge carriers in the semiconductor devices are within the solid itself, while in the earlier vacuum tubes/valves, the mobile electrons were obtained from a heated cathode and they were made to flow in an evacuated space or vacuum. No external heating or large evacuated space is required by the semiconductor devices. They are small in size, consume low power, operate at low voltages and have long life and high reliability.”