Question

a piece of wire is redrawn by pulling it until it is its length is doubled compare the new resistance with the original one​

Answer 1

Answer:

Volume = Area of cross-section x Length

∴ V = A'L' = AL

or A'A = LL' = L2L = 12 [∵ L' = 2L]

∴ Ratio of the resistances are,

R'R = ρL'A'ρLA = L'L× AA' = 21×21 = 4

i.e., R' = 4R

Thus, the new resistance is four times the original resistance.

Answer 2

When

becomes

, A becomes

. New resistance,

(where

is the original resistance). <br> Since the two lamps are in parallel, total power,

<br> Resistance,

<br> Current,