1.

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

Answer»

`1.2xx10^(7)`
`2.4xx10^(7)`
`3xx10^(6)`
`6xx10^(6)`

SOLUTION :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)`


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