1. The electric field inside a sphere having charge density related to the distance from the centre as p=ar (a is a constant) is: ar (a) 4 (b) 4 0 (c) ar 3 (d) none of these 2. A uniform disc of mass 2kg and radius 50mm is released form rest on a smooth incline plane as shown. If the length of incline equals 160cm, the time taken by the disc to arrive at bottom equals (a) 1s 30 (b) 0.8 s (c) 0.6 s (d) 0.5 s 3. In the figure shown below, the maximum and minimum possible unknown resistance (X), that can be measured by the post office box are Xmax and Xmin respectively. Then the ratio of these two resistances is: (In this experiment, we take out only one plug in arm AB and only one plug in arm BC, but in arm AD we can take any no. of plugs): P Q 1000 10010 B10 1001000 5000 2000 1000 100R 200 500 200 www unknown resistance EX (a) 3 x 105 (b) 5 x 105 (c) 7 105 (d) 9 105