(Solved): 4.31 The circular disk of radius a shown in Fig. 4-7 has uniform charge density s across its ...

4.31 The circular disk of radius $$a$$ shown in Fig. 4-7 has uniform charge density $${?}_{\mathrm{s}}$$ across its surface. (a) Obtain an expression for the electric potential $$V$$ at a point $$P=(0,0,z)$$ on the $$z$$-axis. (b) Use your result to find $$\mathbf{E}$$ and then evaluate it for $$z=h$$. Compare your final expression with (4.24), which was obtained on the basis of Coulomb's law. Figure 4-7: Circular disk of charge with surface charge density $${?}_{\mathrm{s}}$$. The electric field at $$P=(0,0,h)$$ points along the $$z$$-direction (Example 4-5).