Engineering Answers

A diffusion couple is made from nickel and iron. After 30 hours of heat treatment at 1400 K, the concentration of nickel is 3.2 wt % at a distance of 1.5 mm from interface. If an identical diffusion couple is heated at 1200 K for 30 hours, at what depth from the interface will the concentration of nickel be 3.2 wt %? The pre-exponential factor (Do) and activation energy for diffusion is 1.8 x 10-5 m2 /s and 152 kJ/mol respectively, and the surface concentration of nickel is 100 wt%. (Note that this is a non-steady state diffusion process

Review Conceptual Example 2 before attempting this problem. The moon has a diameter of 3.48 x 106 m and is a distance of 3.85 x 108 m from the earth. The sun has a diameter of 1.39 x 109 m and is 1.50 x 1011 m from the earth. Determine (in radians) the angles subtended by (a) the moon and (b) the sun, as measured by a person standing on the earth. (c) Determine the ratio of the apparent circular area of the moon to the apparent circular area of the sun. These calculations determine whether a total eclipse of the sun is really “total.”

1.Write v(t) = 10sin(377t+60) as a phasor .

2.Find the pf if v(t) = cos(100t+30) i(t) = sin(100t).

3.Draw the phasor diagram for v(t) = 10cos(100t) i(t) = cos(100t+30)

4.For a power load of 1KW with pF = 0.707 lagging. Draw power triangle.

5.Three capacitors of 10μFare in series. Find equivalent capacitance.

6.A transformer has 600KVA rating. Calculate power delivered at pF = 0.85.

7.Three impedances 1,j1 and j2 are in series. Calculate equivalent resistance and reactance.

8.A source of 10 Volts has an internal impedance of 10-j10. Find the load for maximum power.

1. Use the Cu-Ni phase diagram

(a)Based on the phase diagram, comment on the solubility of Cu and Ni in eachother and explain your answer.

(b)What type of solid solutions are resulting alloys? Explain your answer.

(c)For a Cu-40Ni alloy (60wt%Cu, 40wt%Ni), determine the degrees of freedom and the phase composition at

(i)1300°C

(ii)1250°C

(iii)1200°C

1.Use the Cu-Ag phase diagram.

(a) What is the maximum solubility of Cu in Ag, and at what temperature do you get the maximum solubility?

(b)What is the maximum solubility of Ag in Cu, and at what temperature do you get the maximum solubility?

(c)(i)What transformation is taking place at point E

(ii)At what temperature and composition does the transformation at point E take place?

(iii)What is the significance of the transformation at point E?

(iv) Sketch, label and describr the microstructure formed at point E.

(d) For theCu-Ag alloy, determine

(i)phase composition at 1100°C

(ii)phase composition at 900°C

(iii)phase composition at 600°C

Note: point E is an eutectic point.

For position vector, R=X ax+Y ay+Z az, show that

a) div R=3

b)curl R=0

c)curl[R/R^3]=0

If the potential function,V is given by V=(x^3)y-x(y^2)+3z

convert the following equation written in cartesian coordinate in to an equation of cylindrical coordinates x^3-2x^2-6z=4-2y^2

a closed surface is defined in spherical coordinates by 3<r<5,0•1π<0<•3π,1•2π<Fi<1•6π find the volume enclosed. hint (dv=r^2sina ddr,da,dfi)