wbjee 2009 Question Paper
1. One Kg of copper is drawn into a wire of 1mm diameter and a wire of 2 mm diameter. The resistance of the twowires will be in the ratio (A) 2 : 1 (B) 1 : 2 (C) 16 : 1 (D) 4 : 1, 2. An electrical cable having a resistance of 0.2 Ω delivers 10kw at 200V D.C. to a factory. What is the efficiency of transmission ?..