Current Electricity Charging Discharging Of Capacitors Question 665
Question: The length of a given cylindrical wire is increased by 100% Due to the consequent decrease in diameter, the change in the resistance of the wire will be
Options:
A) 300%
B) 200%
C) 100%
D) 50%
Show Answer
Answer:
Correct Answer: A
Solution:
[a] The new length is 2l if the original length is l. clearly, the new cross-sectional area is $ \alpha /2 $ if a is the initial cross-sectional area. This is because the volume of the wire has to remain constant. Now, $ R\alpha =\rho \frac{21}{9/2}=4R $ This increase in resistance is $ 4R-R=3R. $ The percentage increase in resistance is $ \frac{3R}{R}\times 100= $ 300%
BETA
