Question

A piezoelectric crystal has a coupling coefficient K of 0.32. How much electrical energy must be applied to produce output energy of 7.06 × 10^-3 J?
1. 25.38 mJ
2. 68.94 mJ
3. 4.80 mJ
4. 2.26 mJ

Answer 1

Correct Answer - Option 2 : 68.94 mJ

Concept:

The coupling coefficient of Piezoelectric crystal is given by

\(k = \sqrt {\frac{{{E_o}}}{{{E_i}}}} \)

E_o is the mechanical energy stored (output)

E_i is the electrical energy applied (input)

Calculation:

Coupling coefficient k = 0.32

Output energy = 7.06 × 10^-3 J

The coupling coefficient of Piezoelectric crystal is given by

\( \Rightarrow 0.32 = \sqrt {\frac{{7.06 \times {{10}^{ - 3}}}}{{{E_i}}}} \)

⇒ Electrical energy applied = 68.94 mJ