Question

The working of quartz crystal in the watch is based on
A. Piezo-electric effect
B. Johnson effect
C. Photoelectric effect
D. Edison effect

Answer 1

Hint: The Piezo-electric effect is the phenomenon due to which certain materials generate electric charge when mechanical pressure is applied to them. It is widely used in generation of high voltages, electronic frequency generation and microbalances.

Complete step by step answer:
The working of quartz crystals in the watch is based on piezo-electric effect.
The Piezo-electric effect is the phenomenon due to which certain materials generate electric charge when mechanical pressure is applied to them. When mechanical stress is applied to a piezoelectric material, there is a shifting of the positive and negative charge centres in the material, which then results in an external electrical field. One unique characteristic of this effect is that the reserve of the effect is also observed, i.e: when an electric field is applied to a piezoelectric material, a mechanical stress is also observed in the material. There are many piezoelectric materials that are available, both man-made and natural. Some naturally piezoelectric occurring materials include Berlinite (structurally identical to quartz), cane sugar, quartz, Rochelle salt, topaz etc. Barium titanate and lead zirconate titanate are some examples of man-made piezo-electric materials. The applications of piezo-electric effect are far and wide. It is widely used in generation of high voltages, electronic frequency generation, microbalances and in scientific instrumental techniques with atomic resolution, such as scanning probe microscopes (STM, AFM, etc). It is also used in other day to day objects, like in lighters and in watches.
Hence, the correct option is A.

Note: (i) Edison effect: This effect was discovered by Thomas Edison while he was trying to improve his new incandescent lamp. According to the effect in vacuum electrons flow from a heated element to a cooler metal plate.
(ii) Photo-electric effect: Photoelectric effect was given by Einstein. The photoelectric effect is a phenomenon due to which electrons are emitted from the surface metals when certain frequencies of light are incident upon it.