Tiêu đề 20. Electrostatics QB.pdf ✅

71 EH EduHulk Download Free Study Material from EduHulk.com 1. When an object is positively charged by friction then - (1) object gains some electron (2) object losses some electron (3) object gains some proton (4) object losses some proton 2. When an object is charged with rubbing then its weight (1) reduces (2) increases (3) it may reduce or increase (4) remains constant 3. – 6.4 × 10–17 charge is given to an oil drop then number of electrons in excess is - (1) 4 (2) 40 (3) 400 (4) 4000 4. How many electrons should be removed from an object to gain 1.0 × 10–7 C charge – (1) 1.6 × 1010 (2) 1010 (3) 6.25 × 1011 (4) 6.25 × 1018 5. If 1500 electrons are transferred from one metallic sphere to another of same mass and then 500 electrons are transferred from second sphere to first then the difference of charges on both spheres is - (1) 3.2 × 10–15 C (2) 3.2 × 10–16 C (3) 1.6 × 10–16 C (4) 1.6 × 10–15 C 6. Two equal charges have same mass and force of electrostatic and gravitation are also same then value of q/ m will be – (1) G (2) G 0 F HG I K J (3) 40G (4) G 40 7. If value of charges and distance between them is doubled then new force will be – (1) doubled (2) halved (3) remains unchange (4) 4 times 8. The bob of a simple pendulum is charged and displaced slightly from vertical mean position and released then it produces - (1) An electric field only (2) A magnetic field only (3) Both electric and magnetic fields (4) Electric field, magnetic field and electro magnetic wave 9. In vector form coulomb's law is - (1)  F K q q r  1 2 2 (2)   F K q q r  r 1 2 2 (3)   F K q q r  r 1 2 3 (4)   F K q q r  r 1 2 10. Two point charges + 2 μC and + 6 μ C feeling a force of 12 N. If a charge of – 2 μC is added in both then new force will be - (1) zero (2) 3 N attraction (3) 8 N repulsion (4) 4 N repulsion 11. Four equal charges 2μC each are placed at x-axis just at positions respectively x = 0 , 2, 4 and 8 cm. Find out force on charge at x = 2 cm in newton - (1) 0 (2) 5 (3) 10 (4) 10–2 12. Charge q is given to two identical spheres P and Q. A third uncharged sphere of equal size is touched with two spheres one after another and then removed. The new force of repulsion between spheres will be (initially the force between spheres is F) - (1) 3/4 F (2) 4/9 F (3) 2/3 F (4) 3/8 F 13. Two identical charged sphere A and B repels each other with a force of 8 × 10–6 N. If a third identical uncharged sphere C is touched with sphere A and then placed at the mid point of A and B then net force acting on C is - (1) 4 × 10–6 (2) 8 × 10–6 (3) 2 × 10–6 (4) 10–6 Home Assignment # 1 • Properties of Charge • Coulomb’s Force