# To Determine Young’s Modulus of Elasticity of the Material of a Given Wire - Physics Practical Class 11 Viva Questions with Answers

1. What is elasticity?
2. Answer. The property of a body under which a body tends to regain its original shape or size when external forces are removed is called elasticity.

3. What is the dimension of strain?
4. Answer. Strain is a dimensionless or unitless quantity.

5. Define stress.
6. Answer. Stress is a physical quantity measured as the force per unit area. It is given by the formula: Stress = Force/Area.

7. What are the types of stress?
8. Answer. Types of stress are,

• Longitudinal stress
• Volume stress or bulk stress
• Tangential stress or shear stress
9. What is the unit of stress?
10. Answer. The unit of stress is N/m^2.

11. What is meant by strain?
12. Answer. Strain is the ratio of change in the shape or size of a body to the original shape or size.

13. What is the formula to express Hooke’s law?
14. Answer. Hooke’s law is given by the formula: F = –k.x

Where,

F – force

x – extension length

k – constant of proportionality or spring constant

15. What is the formula to determine the strain?
16. Answer. Strain is given by the formula:

Strain = Change in dimension / Initial dimension

17. What is Young’s modulus of steel?
18. Answer. Young’s modulus of steel is 200 GPa.

19. Consider a wire with length L and radius r loaded with weight Mg where l is the increase in length. What is the formula to calculate the normal stress and longitudinal strain?
20. Answer. Normal stress is given by :

$$\begin{array}{l}\frac{Mg}{\pi r^{2}} \end{array}$$

Longitudinal strain is given by the formula:

$$\begin{array}{l}\frac{l}{L} \end{array}$$

Young’s modulus = Normal stress / Longitudinal strain

=

$$\begin{array}{l}\frac{\frac{Mg}{\pi r^{2}}}{\frac{l}{L}} \end{array}$$

=

$$\begin{array}{l}\frac{MgL}{\pi r^{2}l} \end{array}$$

21. Define Poisson’s ratio.
22. Answer. Poisson’s ratio is defined as lateral strain to longitudinal strain and is denoted by μ.

23. What happens when the object crosses the yield point?
24. Answer. When the object crosses the yield point, permanent plastic deformation takes place.

25. Define Young’s modulus.
26. Answer. Young’s modulus is described as the mechanical property to withstand compression or elongation with respect to its length.

27. What are the types of elastic constants?
28. Answer: Various types of elastic constants are:

29. Bulk modulus (K)
30. Young’s modulus or modulus of elasticity (E)
31. Poisson’s ratio (µ)
32. Shear modulus or modulus of rigidity (G)
33. What is the formula to find Young’s modulus?
34. Answer. The formula to find Young’s modulus is:

$$\begin{array}{l}E=\frac{\sigma}{\epsilon}\end{array}$$

35. What is the SI unit of Young’s modulus?
36. Answer. The SI unit of Young’s modulus is Pascal.

37. Define yield point.
38. Answer. The yield point is defined as the stress beyond which the material becomes plastic.

39. What is meant by tensile strain?
40. Answer. Tensile strain is the change in length of a body due to the application of tensile stress.

41. What is Young’s modulus of lead?
42. Answer. Young’s modulus of lead is 5.5 MPa.

43. When is tangential stress experienced?
44. Answer. Tangential stress is experienced when the elastic restoring force acts parallel to the surface area.