Select the correct statement about polar bonds and dipole moments. a. A linear diatomic molecule AX has a dipole moment equal to the sum of the electronegativities of A -- X.

b. The dipole moment for a polyatomic molecule equals the vector sum of the individual bond moments.

c. The electrons in a polar covalent bond spend more time near the least electronegative atom in the bond.

d. A polyatomic molecule which contains one or more polar bonds always has a molecular dipole moment.

e. A dipole moment quantifies the separation of charge in a molecule using the number of lone pairs on each atom.

Which of the following ziegler nichols tuning methods the response of the controller to a step input should exhibit an s-shaped curve? a)-open loop mode b)-closed loop mode c)-both modes (open & closed) d)-none of the modes (open & closed)

What is the heat treatment of metals? what is the benefit of it? why and how it's useful? answer in details, do not write by hand.

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?