Resistance of a conductor is inversely proportional to the area of its cross section.Why ?
All wire has resistance to some degree. Use ohm's law. R E/I and other variations. Let's take a length of wire with 100 ohms resistance and apply 100 volts. Current (I) 1 amp. So power I x E 100 watts. Let's take another length of wire of the same size and connect it in parallel to the 1st wire and apply 100 volts. Total current will equal 2 amps because we cut the resistance to 1/2 or 50 ohms. Remember the formula for resistors in parallel. So power I x E 200 watts. Because we effectively increased the cross sectional area of the wire by adding a second wire, we've reduced the resistance, and increased power consumption.
from the defination of resistance u can tell this. As it is the obstruction experienced by the flowing electron(current). For wires having less area there is more collision bet the electrons due to less space so more resistance while more area means more space so less collison so less resistance. Just think of cars going on a narrow and wide street where more accidents will slow down others on narrow street while less crashes on wide street will offer less resistance. I equals neAv here increasing area will not increase n if i increases and R equals rho x l/A experimentaly. If a increases then i increases only coz R decreases if R would have increased then obstruction would have also increased but it doesn't.
The answer is surface area. Current travels on the surface of a conductor. Since surface area is where current travels, the greater the cross sectional area, the greater the surface area, the lower the resistance. In fact, a copper pipe makes just as good a conductor as a copper bar. Parallel conductors is a good example. The metal body of a car is used at the current return path in automobiles for the same reason. The large surface area makes the lowest conducting path, and therefor, the ideal ground path. Electricity is not at all like water in a pipe. Current flow is much more like ping pong balls in a pipe. Fill the pipe with ping pong balls. Push one more ball in and one pops instantly out the other end. Voltage pushes electrons, they push the ones next to them and so on. The more surface area, the more electrons, the greater the current flow. It is the crystal structure of metals that makes it all work.
