# Engineering Physics Questions and Answers – Piezoelectricity

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Piezoelectricity”.

1. Piezoelectric effect is when materials produce electric charges when ____________
a) Voltage is applied
b) Mechanical Stress is applied
c) Electric field is applied
d) Magnetic field is applied

Explanation: Certain materials produce electric charges on their surface when mechanical stress is applied on them. This effect is called piezoelectric effect.

2. Piezoelectricity means _________________
a) Electric polarization
b) Electric dielectric
c) Pressure electricity
d) Polar dielectric

Explanation: The word piezo means pressure. Thus, piezoelectricity is also called pressure electricity as the application of pressure on certain material induces electricity in them.

3. All Piezoelectric materials are Ferroelectric.
a) True
b) False

Explanation: All the ferroelectric materials are pyroelectric and piezoelectric but the reverse is not true. Ferroelectricity can occur only in noncentrosymmetric crystals, just like piezoelectricity.

4. The piezoelectric materials used for converting energy are called as ___________
a) Transition Devices
b) Converter
c) Dielectric
d) Transducer

Explanation: The piezoelectric effect is often used to convert electrical energy into mechanical energy and the piezoelectric materials used are called transducers.

5. Piezoelectricity is shown by substances which are ___________
a) Polar
b) Non-polar
c) Symmetric
d) Asymmetric

Explanation: Piezoelectricity is shown by the substances which are asymmetric. If a center of inversion is present and it persists even after stress is applied, the net polarization remains zero.
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6. No regular cubic lattice can exhibit piezoelectricity.
a) True
b) False

Explanation: A cubic lattice is highly symmetric. Even after the application of stress, it has a center of inversion. Thus, it cannot exhibit piezoelectricity.

7. What is X-Y from the following graph?

a) 1
b) 2
c) 3
d) 4

Explanation: There are 32 symmetry point groups out of which 21 (X) are Noncentrosymmetric and out of them 20 (Y) are Piezoelectric. Thus, X – Y = 1.

8. Piezoelectric effect is ___________
a) Isotropic
b) Anisotropic
c) Large in Magnitude
d) Dominating

Explanation: Piezoelectric effect is anisotropic. Since there is a lack of a center of inversion and complex structure of piezoelectric, it is different in different directions.

9. Which of the following is the correct expression for Piezoelectric effect?
a) P = Zd + E
b) P = Zd + εoE
c) P = Zd + εoχE
d) P = Zd + dεoχE

Explanation: The correct expression for the piezoelectric effect is: P = Zd + εoχE, where P is the polarization, Z is the stress, d is the piezoelectric strain constant, E the electric field and χ the electric susceptibility.

10. The piezoelectric strain can be shown as ___________
a) deik/dZ
b) deik/dχ
c) deik/dEi
d) deik/dε

Explanation: In practice, the tensile or compressional or shear strains develop in different direction due to an applied electric field depending on the crystal orientation and field direction. The expression for strain is: deik/dE.

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