A uniformly charged disc of radius R having surface charge density σ is placed in the xy plane with its center at the origin. Find the electric field intensity along the z-axis at a distance Z from origin :
1
\(E = \frac{\sigma }{{2{\varepsilon _0}}}\) \(\left( {1 + \frac{Z}{{{{\left( {{Z^2} + {R^2}} \right)}^{1/2}}}}} \right)\)
2
\(E = \frac{\sigma }{{2{\varepsilon _0}}}\) \(\left( {1 - \frac{Z}{{{{\left( {{Z^2} + {R^2}} \right)}^{1/2}}}}} \right)\)
3
\(E = \frac{{2{\varepsilon _0}}}{\sigma }\) \(\left( {\frac{Z}{{{{\left( {{Z^2} + {R^2}} \right)}^{1/2}}}} + Z} \right)\)
4
\(E = \frac{\sigma }{{2{\varepsilon _0}}}\) \(\left( {\frac{Z}{{{{\left( {{Z^2} + {R^2}} \right)}}}} + \frac{1}{{{Z^2}}}} \right)\)