(a) The radius of a conducting wire AB uniformly decreases from its one end A to another end B. It is connected across a battery. How will (i) electric field, (ii) current density, and (iii) mobility of electrons change from end A to end B ? Justify your answer in each case. OR (b) Two large plane sheets $P_1$ and $P_2$ having charge densities $+\sigma$ and $-3\sigma$ respectively are arranged parallel to each other as shown in the figure. Find the net electric field $(\vec{E})$ at points A, B and C.