Question

resistance of a conductor wire of length 1m and area of cross section 0.2 cm square is 10 ohm the resistance of wire of same material of length 3m and area of cross section 0.2 cm is ? ​

Answer 1

Answer:

resistance of second wire = 3.333........ ohm

Explanation:

resistance of first wire,r = 10 ohm

area of cross section ,a = 0.2 cm^2

length of wire,l = 1 m = 100 cm

resistivity of wire,R = ?

∴ r = Ra/l

R = rl/a                               ----(1)

let the resistance of second wire = r'

length ,l' = 3 m = 300 cm

area of cross section , a' = 0.2 cm^2

resistivity of wire is same as the first wire because the wire is made up of same material

r' = Rl'/a'

R = r'l'/a'                                  ----(2)

therefore eq. (1)=(2)

rl/a  = r'l'/a'  

r' = rl/a ×a'/l'

r' = 10*100/0.2 × 0.2 /300

r' = 10/3 = 3.3333.......