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JEE Main2008PhysicsCurrent ElectricityActual

Paragraph: Consider a block of conducting material of resistivity ' ' shown in the figure. Current 'l' enters at 'A' and leaves from ' D '. We apply superposition principle to find voltage ' V ' developed between ' B ' and ' C '. The calculation is done in the following steps: (i) Take current 'l' entering from 'A' and assume it to spread over a hemispherical surface in the block. (ii) Calculate field E(r) at distanc

Options

  1. Al a - l (a+b)
  2. Bl a - l (a+b)
  3. Cl 2 a - l 2 (a+b)
  4. Dl 2 (a-b)

Correct answer

C. l 2 a - l 2 (a+b)

Step-by-step solution

Choosing A as origin, gathered E= j= 1 2 r^2 V_C-V_B=- l 2 _a^ (a+b) 1 r^2 d r= l 2 [ 1 (a+b) - 1 a ] V_B-V_C= l 2 [ 1 a - 1 (a+b) ] gathered

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