Answer #32

The correct answer is C: The effect involves transformation of electrical energy to mechanical energy.

By definition a substance that exhibits the piezoelectric effect is one that can convert electrical energy to mechanical energy (ultrasound) and can also convert mechanical energy back into electric energy. Therefore by definition it is bidirectional. Naturally occurring substances have poor efficiency and can be modified to increase sensitivity and bandwidth, using high temperatures and magnetic fields to align the crystal lattice in a process called "poling". Quartz exhibits the piezoelectric effect, but not very efficiently.