Question

A wire of length = l and resistance = R , if it streched such that its length becomes 3 times more of its initial one. Find the ratio of initial resistance to the newly obtained resistance.​

Answer 1

Answer:

1:3 is the required answer

Explanation:

According to the Question

It is given that ,

Length of wire = l

Resistance ,R

Resistance in 1st case :-

R = ρl/A

where

R denote Resistance

ρ denote electrical resistivity

l denote length of wire

A denote Area of cross section .

→ R = ρl/A ------------(i)

Again in second case the wire is stretched such that it's length become 3 times as initial was .

New length of Wire = 3l

Resistance in 2nd case :-

→ R = ρ3l/A -----------(ii)

From equation (i) & (ii) we get

→ ρl/A = ρ3l/A

→ l = 3l

→ 1 = 3

Hence, the ratio of initial resistance to the newly obtained resistance will be 1:3 .

Answer 2

Answer:

Length (l) is doubled & Area of cross section (A) is halved. l becomes 2l & A becomes A/2 R = PL/A now take l = 2l,A = A/2 R = P2l/A/2 = 4PL/A 4R Resistance ...