Question

Illustration 4.
The current density at a point is j = (2x10^ſ) Am 2.
Find the rate of charge flow through a cross sectional area Š = (2 +3h) cm?​

Answer 1

Explanation:

we know, relation between current (i) , current density (\vec{J}

J

) and cross sectional area (\vec{A}

A

) is given by,

i=\vec{J}.\vec{A}i=

J

.

A

here it is given that , \vec{A}

A

= (2i + 3j+ 0k) mm² = (2i + 3j) × 10^-6 m²

and \vec{J}

J

= (0i + 3j + 4k) A/m²

now, i = (2i + 3j + 0k) × 10^-6 .(0i + 3j + 4k) A

= (2 × 0 + 3 × 3 + 0 × 4) × 10^-6

= 9 × 10^-6 A = 9\mu AμA

hence, current through the area is 9\mu AμA

Hope it's helpful for you