Electrostat-08-Answersheet

1. (a) 2. (a) 3. (b) 4. (b) 5. (b) 6. (b) 7. (d) 8. (b) 9. (c) 10. (b) 11. (d) 12. (d) 13. (c) 14. (b) 15. (a) 1. (c) 2. (c) 3. (c) 4. (b) 5. (b) 6. (a) 7. (c) 8. (d) 9. (b) 10. (b) 11. (c) 12. (b) 13. (c) 14. (b) 15. (b) 1. (a) r  12 102 m (b) 0.2 N (attractive) 2. 2 3 unit 3. (a) 54 × 104 N C-1 along O B (b) 81 × 10–5 N C-1 along B A 4. Total charge is zero. Dipole moment = 7.5 × 10-6 Cm along z-axis. 5. Charges 1 and 2 are negative charge 3 is positive particle 3 has the highest charge to mass ratio. 6. (a) 30 N m2/C. (b) 15 N m2/C. 7. 1.9 × 108 N m2/C. 8. (a) A plane normal to AB and passing through its mid point has zero potential every- where. (b) Normal to the plane in the direction AB. 9. (a) Zero (b) 105 NC-1. (c) 5 × 103 NC-1. 10. (a) 3 P F (b) 40 V 11. (a) Potential = 4q / 3πε0 (b) field is zero, as expected by symmetry. 12. 10-4 N m 13. (a) 1.5 × 10-2 N (b) 0.24 N 14. (a) 9 pF (b) 200 pC, 300 pC and 400 pC 15. 1.2 J ; The point R is irrelevant to the answer. SUBJECTIVE LEVEL - II 1. 52 sec. 16π3ε mR 3 1 / 2 2. t   0   Qq  3. K = 2 4. q  8.71108 C 5. 48 C on 8F and 24C on each 4F . 6. 125 mC 7. 43 mV 8. 3 : 5  2 9. 0 1  a   d  2d  A0 10. a  b 1. (a)   1b a 5 / 2 . (b) q  0  1ba5/ 2 2. (a) q 4πε 0 d 2 1 (b) P 4πε 0 d3 (c) q  4πε 0 d3 l q 2d 2  p 2  3. 1   . ε 0  l 2  R 2  4. (a) 50/3 V at each point (b) zero. 5. (a) 10 1010 F 3 q2 (b) 104 1010 F . 30 A V2  1 1  x  x   0    6. (a) 2A0 (b) 2  x1 x2  7. (a) t  2 d 3 (b) U  1 A0 V2 , U i 2 d f  1 KA0 V2 2 d 8. (a) 0.5 mC (b) 104 V 9. T  8 ε AV 2  2 3 / 2 10. (a) 0 , (b)  d 0  2d 2 d 0  d1   3  1. u = 5.86 m/s. H   4 a H  2. (a)  3  (b) U  3mga at   3. vmin  Q2 R   R n  2 Q 2 R 4. (a) Un  8πε r 2 1   R  r   (b) Un n  2 0     0 5. i  4.43 109 A 6. (a) (b) (c) CA  2.0 10 9 F , VA  1.21 105 J W  4.84 105 J U  1.1105 J 7. σ'  5σ 6