Ncert Exercises & Solutions

An infinitely long thin wire carrying a uniform linear static charge density $λ$ is placed along the z-axis (figure). The wire is set into motion along its length with a uniform velocity v = $v {\hat{k}}_{z}$ Calculate the pointing vector $S = \frac{1}{μ_{0}} (E \times B) .$

Hint: The Poynting vector is given by;

\vec{S} = \frac{1}{μ_{0}} [\vec{E} \times \vec{B}]

Step 1: Find the electric field and the magnetic field.

Given, \vec{E} = \frac{λ}{2 {πε}_{0} a} \hat{j}

\vec{B} = \frac{μ_{o} i}{2 πa} \hat{i} = \frac{μ_{o} λv}{2 πa} \hat{i}

Step 2 : Find the poynting vector .

∴ \vec{S} = \frac{1}{μ_{0}} [\vec{E} \times \vec{B}] = \frac{1}{μ_{0}} [\frac{λ}{2 {πε}_{0} a} \hat{j} \times \frac{μ_{0}}{2 πa} λ \hat{i}]

= \frac{λ^{2} v}{4 π^{2} ε_{0} a^{2}} (\hat{j} \times \hat{i}) = - \frac{λ^{2} v}{4 π^{2} ε_{0} a^{2}} \hat{k}

NEET Information

courses

Company

Botany Questions

Chemistry Questions

Physics Questions

Zoology Questions