Question

a long straight wire of resistance R , radius 'a' and length 'L' Carrie's a constant current 'I' .The poynting vector for the wire is​

Answer 1

Answer:

Explanation:

Since,

Electric field in wire,

E = $\frac{V}{L}$ = $\frac{I R}{L}$                 [  V = I R ohm's law  ]

and

H = $\frac{I}{2\pi r }$        (current distributed along surface of wire)

So, magnitude of poynting vector,  

S = ER - $\frac{I^{2} R }{2 \pi\alpha L }$