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Resistance is defined as the property of a substance due to which it opposes the flow of Electricity i.e electrons through it. Metals, acids and salts are the good conductors of electricity. These free or loosely attached electrons (vagrant) while flowing pass through the molecules or the atoms of the conductor,collide and other atoms and electrons, thereby producing heat. The unit of Resistance The practical unit of resistance is ohm. A conductor is have a resistance of one ohm if it permits one ampere current to flow through it when one volt is applied through its terminals. The unit of resistance is ohm. Laws of Resistance  The resistance R offered by a conductor depends on the following factors: 1. It varies directly as its length l. 2. It varies inversely as the cross section A of the conductor. 3. It depends on the nature of the material. 4. It also depends on the temperature of the conductor. R= ρ.l/A where,   ρ is a constant de...

(Solve Any 3rd Degree Polynomial Equation) I'm putting this on the web because some students might find it interesting. It could easily be mentioned in many undergraduate math courses, though it doesn't seem to appear in most textbooks used for those courses. None of this material was discovered by me. -- ES You should know that the solution of ax2+bx+c=0 is There is an analogous formula for polynomials of degree three: The solution of ax3+bx2+cx+d=0 is (A formula like this was first published by Cardano in 1545.) Or, more briefly, x   =   {q + [q2 + (r-p2)3]1/2}1/3   +   {q - [q2 + (r-p2)3]1/2}1/3   +   p where p = -b/(3a),    q = p3 + (bc-3ad)/(6a2),    r = c/(3a) But I do not recommend that you memorize these formulas. Aside from the fact that it's too complicated, there are other reasons why we don't teach this formula to calculus students. One reason is that we're trying to avo...