Among cis-But-2-ene & trans-But-2-ene, Which one is polar? Why??

In this video, Let us discuss polarity of geometrical isomers. Polarity of a compound can be predicted from dipole moment. Dipole moment = Charge x distance of separation In chemistry dipole moment is represented by the crossed arrow , the cross is on positive side and arrow head is on the negative part of compound. Generally, Dipole moment increases with increasing electronegativity and increasing bond length. When we compare dipole moment of Cis, Trans isomer, due to similar arrangement, they both have equal magnitude of charge. Here, we need to remember that, Dipole moment is a vector quantity depends both on magnitude of charge and direction of dipole. In Cis isomer, the direction of dipole of two C-CH3 individual dipole, all lie in the same direction. Therefore, net dipole, the sum of all individual dipole, increases. But, In Trans isomer, the direction of dipole of all 2 C-CH3 bonds , all not lie in the same direction. They are opposite to each other. They cancel each other, thus making the trans form non-polar.. Hence Cis form of alkene is polar.