A cylindrical conductor of diameter 0.1 mm carries a current of 90 mA. The current density( in `Am^(-2)`) is `pi= 3`

Options

A. `1.2xx10^(7)`
B. `2.4xx10^(7)`
C. `3xx10^(6)`
D. `6xx10^(6)`

Answer

A

Explanation

Diameter of cylindrical conductor (D) = 0.1 mm
Radius (r ) `= (D)/(2)=(0.1)/(2)mm`
Current (I) = 90 mA `= 90xx10^(-3)A`
We know that,
Current density `(J)=(I)/(A)`
`= (I)/(pi r^(2))`
`= (90xx10^(-3))/((22)/(7)xx((0.1xx10^(-3))/(2))^(2))`
`= (90xx10^(-3))/(3.14xx((0.1xx10^(-3))/(2))^(2))`
`= 12000xx10^(3)`
`= 1.2xx10^(7)A//m^(2)`