Passage-III : If the ends of a rod are rigidly clamped so as to prevent any actual expansion or contraction and then the temperature of the rod is changed, the rod will develop tensile or compressive stress or thermal stress. This type of stress sometimes could be adequate to cause permanent strain or also break the rod. To avoid damages for the above said reasons concrete highways are always left with gasps between the section for the expansion or contraction of concrete In a similar way, if the temperature of an object under pressure is increased but the object is not allowed to expand, the pressure will also increase. Assuming a negative sign for a compressive stress and positive sign for tensile stress, answer the following questions Consider a rod rigidly clamped at its ends. As the temperature is increased, which of the following statement(s) is/are correct?

Which of the following ways are suitable for increasing food production? I) Agrochemical based agriculture. II) Organic agriculture. III) Genetically engineered crop-based agriculture. Choose the correct option.

Covalent molecules formed by heteroatoms bound to have some ionic character. The ionic character is due to shifting of the electron pair towards A or B in the molecule AB. Hence, atoms acquire small and equal charge but opposite in sign. Such a bond which has some ionic character is described as polar covalent bond. Polar covalent molecules can exhibit dipole moment. Dipole moment is equal to the product of charge separation, q and the bond length, d for the bond. The unit of dipole moment is Debye. One Debye is equal to 10^(-18) esu cm. Dipole moment is a vector quantity. It has both magnitude and direction. Hence, dipole moment of molecules depends upon the relative orientation of the bond dipoles, but not on the polarity of bonds alone. A symmetrical structure shows zero dipole moment. Thus, dipole moments help to predict the geometry of the molecules. Dipole moment values can be used to distinguish between cis-and traps-isomers, ortho-, meta-and para-forms of a substance, etc. The percentage of ionic character of a bond can be calculated by the application of the following formula : % " ionic character " = ("Experimental value of dipole moment ")/("Theoretical value of dipole moment ") xx 100 Arrange the following compounds in increasing order of dipole moments, toluene (I), o- dichlorobenzene (II), m-dicblorobenzene (III) and p dichlorobenzene (IV) :