(a) Using Gauss's law, deduce an expression for electric field at a point due to a uniformly charged infinite plane thin sheet. (b) Two large thin plane sheets, each having surface charge density $\sigma$, are held close and parallel to each other in air. What is the net electric field at a point (i) inside and (ii) outside, the sheets ? OR (a) Obtain the condition of balance of a Wheatstone bridge. (b) Find net resistance of the network of resistors connected between A and B, as shown in figure. [Diagram]