What's the factors affecting resistance of a wire? and why? thank you!
i) Cross-sectional area of the wire. Reistance is inversely proportional to the area of cross-section of the wire. More the cross-sectional area, easier it is for the electrons and hence charge to flow and hence more current and less resistance. ii) Length of the wire. Resistance is directly proportional to the length of the wire. More the length of the wire, longer is the distance to be covered by the electrons and hence charge thereby reducing current and increasing resistance. iii) Temperature. Higher temperature results in higher resistance. Higher the temperature, faster will be the oscillations of the ions in the conductor and the moving electrons will have to undergo more number of collisions per unit length of the wire, thereby reducing time between successive collisions and reducing drift velocity of the electrons which results in less current and higher resistance iv) Material of the conductor Some materials like metals are better conductors of electricity and offer less resistance to the flow of current. Non-metals have poor conductivity. Conductivity of charge in metals is mainly due to the free electrons in the outer orbits of metals.
Factors Affecting Resistance
The 2nd and 3rd discussions were good but didn't discuss magnetism. The 1st guy: an open circuit has infinite resistance. Even a straight piece of wire has some self-inductance (or self-magnetism). One affect of inductance is that it opposes changes in current. So when you first apply a dc voltage across a wire and a dc current starts to flow, the self-inductance will resist the increase in current. It will appear to be because of higher resistance than expected. But the current will increase over a short time, and once it gets to a steady-state, the apparent resistance from the self-inductance is zero. This, self-inductance in a straight piece of wire, is a minor affect compared to components that presumably are in the circuit. After the current reaches steady state, the self-inductance will try to oppose a decrease in current. If the voltage and therefore the current are ac - alternating, this gets more complicated. The current is always trying to change. At the level of study I think you are, you should save this for later.
