State the laws of resistance.
Laws of resistance :
1. Resistance of a conductor is directly proportional to its length R α 1
2. Resistance of a conductor is Inversely proportional to its area of cross-section R α 1/a
3. Resistance of a conductor depend upon its nature i.e. copper has less resistance than iron.
4. Resistance of a conductor increases with increase in temperature i.e. resistance of filament of a bulb is more when lighted as compared to when it is not lighted.