Titanic விபத்திற்கு இதுதான் காரணமா
7 Minutes
Piezoelectric effect for students: learn how gas lighters work and how sonar uses quartz crystals to find objects. A Tamil science lesson.
- Dismantling a gas lighter to see the hammer, spring, and crystal
- How compressing a quartz crystal shifts charges to make voltage
- Reverse piezoelectric effect and how sonar uses ultrasound waves
What this lesson teaches
The piezoelectric effect is the generation of electric voltage when mechanical pressure is applied to certain crystals, such as quartz. These materials can also do the opposite in what is called the reverse piezoelectric effect, where applying an electric current makes the crystal rapidly squeeze and expand.
Inside a gas lighter
- A spring and a bent metal hammer rest inside a plastic casing.
- Pressing the trigger pulls the spring tight until the hammer releases suddenly.
- The hammer strikes a quartz crystal with high force, generating around 800 volts of electricity.
- This electrical charge travels through an electrode to the outer metal casing, jumping across the gap as a spark to ignite gas.
How pressure creates electricity
Quartz is made of silicon and oxygen atoms arranged in repeating unit cells that form an asymmetric crystal. In its resting state, the positive charges on silicon and the negative charges on oxygen balance out, leaving the crystal electrically neutral. When mechanical force compresses the crystal, the centers of positive and negative charges shift apart. This separation of charges creates an electric dipole, which forces electric current to flow through attached electrodes.
The reverse effect and sonar
When an alternating electrical voltage is applied across a quartz crystal, it rapidly contracts and expands in rhythm with the signal. Squeezing and expanding tens of thousands of times each second produces high-frequency ultrasound sound waves. In sonar systems, these ultrasound waves travel through sea water and reflect off underwater objects. By measuring the time taken for the echo to return, instruments can calculate the exact distance to submerged objects.
Why it matters
Discovered in the 1880s by Pierre and Jacques Curie, piezoelectricity solved major underwater navigation problems. During World War I, navies began using sonar to locate hidden enemy submarines beneath the ocean surface. Sonar can also detect giant underwater hazards like icebergs well in advance, which could have prevented maritime disasters such as the sinking of the Titanic.