The resistance of a conductor of diameter d and length l is R Ω. If the diameter of the conductor is halved and its length is doubled, the resistance will be
A. R Ω
B. 2R Ω
C. 4R Ω
D. 8R Ω
As per law of resistance, the resistance of the conductor is inversely proportional to its cross-sectional area i.e. it is inversely proportional to the square of the diameter of cross-sectional area of the conductor. As per same law of resistance, the resistance of the conductor is directly proportional to the length of the conductor.