Consider a block of conducting material of resistivity $ \rho$ shown in the figure. Current I enters at A and leaves from D. We apply superposition principle to find voltage $ \Delta V$ developed between B and C. The calculation is done in the following steps. \[\] (i) Take current I entering from A and assume it to spread over a hemispherical surface in the block. \[\] Calculate field E(r) at distance r from A by using ohm's law $E= \rho j$, where j is the current per unit area at r. \[\] (iii) From the r dependence of E(r) obtain the potential V(r) at r. \[\] (iv) Repeat (i), (ii) and (iii) for current I leaving D and superpose results for A and D \[\] For current entering at A, the electric field at a distance r from A is - Clay6.com, a Free resource for your JEE, AIPMT and Board Exam preparation

Consider a block of conducting material of resistivity $ \rho$ shown in the figure. Current I enters at A and leaves from D. We apply superposition principle to find voltage $ \Delta V$ developed between B and C. The calculation is done in the following steps. \[\] (i) Take current I entering from A and assume it to spread over a hemispherical surface in the block. \[\] Calculate field E(r) at distance r from A by using ohm's law $E= \rho j$, where j is the current per unit area at r. \[\] (iii) From the r dependence of E(r) obtain the potential V(r) at r. \[\] (iv) Repeat (i), (ii) and (iii) for current I leaving D and superpose results for A and D \[\] For current entering at A, the electric field at a distance r from A is