Question

A wire of given material having length land area of cross section A has a resistance 28 ohm. What would be the resistance of another wire of same material having length 31 and area of 4 A.​

Answer 1

lenght = l

Area = A

let resistivity be constant

therefore ;

R = p*l/A

i.e. p*l/A = 28 ohms .... (i)

Now

R = p*3l/4A

R = 3/4*p*(l/A)

i.e. 3/4*p*(l/A) = 3/4*28 = 3 * 7 = 21 ohms ( Answer )