NEET Class neet Answered

Resistance R of wire is directly proportional to length L and inversely proportional to cross section area A.

R = ρ × ( L/A)

where ρ is resistivity of material.

If area of cross section is doubled , then cross section area is increaed by 4 times.

Hence new resistance R_new if length and radius of cross section are doubled , then we get

R_new  = ρ × [ ( 2L) / ( 4A) ] = (1/2) ρ × ( L/A) = (1/2) R

Hence by doubling the length and radius of cross section , new resistance decreases to half of its initial value