A wire of length L and diameter D has a resistance R. If the length and the diameter of the same wire are decreased to half of their original values, the resistivity of the new wire

a. doubles.
b. drops to half its original vale.
c quadruples
d. drops to one quarter its original value.
e. remains the same.

e. remains the same

Explanation:

The resistance of a wire, depends on three parameters: the length, the circular cross-sectional area, and the resistivity.The resistivity -assumed the resistor is in the linear zone of operation- is constant, and depends exclusively on the material from which the wire is manufactured.So, if the length and the diameter are modified, the resistivity doesn't change.The option e) is the right one.

Is there any opitions? if you have the periodic table, the noble gases are 8a family, the halogen are the 7a family, and the nonmetal are  carbon, nitrogen, phosphorus, oxygen, sulfur, selenium, fluorine, chlorine, bromine, iodine and astatine.

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.