1. Gaussian error function in denoted as ef.
a) True
b) False
Explanation: Gaussian error function is denoted by the erf and its corresponding values can be found from standard mathematical tables. It is used to find the solution of Fick’s second law.
2. On which of the following does diffusion not depend on?
a) Temperature
b) Pressure
c) Concentration difference
d) Diffusion distance
Explanation: Diffusion depends on the temperature, concentration difference as atoms diffuse from higher concentration region to lower concentration region, diffusion distance. It does not depend on pressure.
3. When something burns on the stove in the kitchen, the whole kitchen starts smelling smoky due to diffusion.
a) True
b) False
Explanation: When something burns on the stove, the atoms of the burnt food starts spreading in the kitchen by random atomic motion by the process of diffusion. The burnt food atoms start moving from places where their concentration is high to regions of low concentration.
4.If we increase the temperature, how is the diffusion rate affected?
a) Diffusion rate increases
b) Diffusion rate decreases
c) Diffusion rate decreases drastically
d) Diffusion rate is not affected
Explanation: As the temperature increases, the kinetic energy of particles increases and hence they start moving randomly faster. Due to the increase in energy the particles bounce again each other faster and start spreading evenly throughout the volume.
5. How is the diffusion rate affected by concentration difference?
a) Diffusion rate is not affected
b) Higher the concentration difference, higher the diffusion rate
c) Lower the concentration difference, higher the diffusion rate
d) Higher the concentration difference, lower the diffusion rate
Explanation: The particles tend to move from higher concentration region to lower concentration difference. Therefore, higher the concentration difference, higher is the rate of diffusion.
6. How is diffusion rate related to diffusion distance?
a) Directly related
b) Inversely related
c) Not related
d) Directly related to square of diffusion distance
Explanation: The diffusion rate is inversely proportional to the distance from which the particles are diffusing. Larger the diffusion distance, the rate of diffusion is slower and vice versa
7. How is the rate of diffusion affected by the weight of diffusing atom?
a) Lighter atoms diffuse faster
b) Heavier atoms diffuse faster
c) Lighter atom diffuses slower
d) Rate of diffusion doesn’t depend on weight of diffusing atom
Explanation: At a given temperature, average energy of atoms is equal and hence the rate of diffusion will depend on the size and weight of the diffusing atom. A lighter atom will diffuse faster than a heavier atom.
8.Diffusion is slower for _________
a) Open crystal structure
b) Low density materials
c) Materials with lower melting temperature
d) Materials with covalent bonding
Explanation: Diffusion rate is high for open crystal structure, material with low density as there is a sample amount of free space to diffuse into and material with low melting temperature as the particles reach liquid state faster and hence diffusion rate increases. On the other hand, the rate of diffusion for materials with covalent bond is slower because they are stronger bonds.
9. Diffusion is slower in polycrystalline structure than single crystalline structure.
a) True
b) False
Explanation: The diffusion rate is faster in a polycrystalline structure than a single crystalline structure. This is because diffusion through grain boundaries is faster than volume diffusion.
10. Up to which point on the stress-strain curve is Hooke’s law valid?
a) Elastic limit
b) Yield point
c) Proportionality limit
d) Fracture point
Explanation: The proportionality limit is the point up till which the strain of an elastic body is proportional to the stress applied on it. While elastic point is the point up till which the elastic properties last. After fracture point the body breaks.