Question

iron has a circular cross section of radius 1 mm and resistivity of its material is 2 into 10 raise to minus 6 find the length of whose resistance is 20 Ohm​

Answer 1

Explanation:

given radius =r = 1mm =

${10}^{ - 3} m$

resisitivty =$ =

$2 \times {10}^{ - 6}$

length =l = ? , resistance R= 20 ohm .

using formula R=$l/a

Area = a =

$\pi {r}^{2}$

therefore a =

$3.14 \times {10}^{ - 6} m {}^{2}$

therefore ,

length = l = a × R / $

l = 31.4 meter ...