Tiêu đề ELECTRIC CHARGES AND FIELDS.docx.pdf ✅

1.ELECTRIC CHARGES AND FIELDS Single Correct Answer Type 1. A polythene piece, rubbed with wool, is found to have negative charge of 4×10 C. the number of electrons −7 transferred from wool to polythene is a) 1. 5×10 12 b) 2. 5×10 12 c) 2. 5×10 13 d) 3. 5×10 13 2. The intensity of electric field at a point between the plates of a charged capacitor a) Is directly proportional to the distance between the plates b) Is inversely proportional to the distance between the plates c) Is inversely proportional to the square of the distance between the plates d) Does not depend upon the distance between the plates 3. Four metal conductors having different shapes I. A sphere II. Cylinder III. Pear IV. Lightning conductor are mounted on insulating stands and charged. The one which is best suited to retain the charges for a longer time is a) 1 b) 2 c) 3 d) 4 4. Three charges –q and are placed as shown in figure. The component of the force on is 1 , + q 2 − q 3 x –q 1 proportional to a) sinθ q 2 b 2 − q 3 b 2 b) cos θ q 2 b 2 − q 3 b 2 c) sinθ q 2 b 2 + q 3 b 2 d) cos θ q 2 b 2 + q 3 b 2 5. According to Gauss’ Theorem, electric field of an infinitely long straight wire is proportional to a) r b) 1/r 2 c) 1/r 3 d) 1/r 6. An electric dipole has a pair of equal and opposite point charges q and –q separated by a distance2x. The axis of the dipole is defined as a) Direction from positive charge to negative charge b) Direction from negative charge to positive charge c) Perpendicular to the line joining the two charges drawn at the centre and pointing upward direction d) Perpendicular to the line joining the two charges drawn at the centre and pointing downward direction 7. The Gaussian surface for calculating the electric field due to a charge distribution is Page| 1
a) Any surface near the charge distribution b) Always a spherical surface c) A symmetrical closed surface containing the charge distribution, at every point of which electric field has a single fixed value d) None of the given options 8. Two charged spheres of radii 10 cm and 15 cm are connected by a thin wire. No charge will flow, if they have a) The same charge on each b) The same potential c) The same energy d) The same field on their surface 9. Three charges each of + 1μCare placed at the corners of an equilateral triangle. If the force between any two charges be F, then the net force on either charge will be a) 2 F b) F 3 c) 2F d) 3F 10. The work done in carrying a charge of 5μC from a point A to a point B in an electric field is 10mJ. The potential difference (V is then B − V A ) a) + 2kV b) − 2 kV c) + 200 V d) − 200 V 11. A parallel plate condenser has a uniform electric field E(V/m) in the space between the plates. If the distance between the plates is d(m) and area of each plate is A(m the energy (joules) stored in the 2 ) condenser is a) 1 2 ε 0 E 2Ad b) E 2Ad/ε 0 c) 1 2 ε 0 E 2 d) ε 0 EAd 12. Two capacitors each of 1μF capacitance are connected in parallel and are then charged by 200 volts d. c. supply. The total energy of their charges (in joules) is a) 0.01 b) 0.02 c) 0.04 d) 0.06 13. Identify the wrong statement in the following. Coulomb’s law correctly described the electric force that a) binds the electrons of an atom to its nucleus b) binds the protons and neutrons in the nucleus of an atom c) binds atoms together to form molecules d) Binds atoms and molecules to from solids 14. When one electron is taken towards the other electron, then the electric potential energy of the system a) Decreases b) Increases c) Remains unchanged d) Becomes zero 15. All capacitors used in the diagram are identical and each is of capacitance C. Then the effective capacitance between the points A and B is a) 1. 5C b) 6C c) C d) 3C Page| 2
16. A uniformly charged thin spherical shell of radius R carries uniform surface charge density of σ per unit area. It is made of two hemispherical shells, held together by pressing them with force F (see figure). F is proportional to a) 1 ε 0 σ 2R 2 b) 1 ε 0 σ 2R c) 1 ε 0 σ 2 R d) 1 ε 0 σ 2 R 2 17. The figure shows the path of a positively charged particle 1 through a rectangular region of uniform electric field as shown in the figure. What is the direction of electric field and the direction of particles 2, 3 and 4 a) Top; down, top, down b) Top; down, down, top c) Down; top, top, down d) Down; top, down, down 18. The capacitance of a metallic sphere will be 1μF, if its radius is nearly a) 9km b) 10m c) 1. 11 m d) 1. 11 cm 19. In the following diagram the work done in moving a point charge from point P to point A, B and C is respectively as W and then A , W B W C , a) W A = W B = W C b) W A = W B = W C = 0 c) W A > W B > W C d) W A < W B < W C 20. The electric field at a point on equatorial line of a dipole and direction of the dipole moment a) Will be parallel b) Will be in opposite direction c) Will be perpendicular d) Are not related 21. A solid sphere of radius R and volume charge density is enclosed by a hollow sphere of radius 1 ρ = ρ 0 r R 2 with negative surface charge densityσ, such that the total charge in the system is zero,ρ is a positive 0 constant and r is the distance from the centre of sphere. The ratio is R 2 R 2 a) σ ρ 0 b) 2σ/ρ 0 c) ρ 0 /2σ d) ρ 0 σ 22. The voltage of clouds is 4×10 with respect to ground. In a lightening strike lasting a 6 volt 100 m sec, charge of 4 coulombs is delivered to the ground. The power of lightening strike is a) 160 MW b) 80 MW c) 20 MW d) 500 KW 23. Two point charge − q and + q/2 are situated at the origin and at the point (a, 0, 0) respectively. The point along the X-axis where the electric field vanishes is a) x = a 2 b) x = 2a c) x = 2a 2−1 d) x = 2a 2+1 Page| 3
24. A 6μF capacitor is charged from 10 volts to 20 volts. Increase in energy will be a) 18×10 −4 J b) 9×10 −4 J c) 4. 5×10 −4 J d) 9×10 −6 J 25. A ring of radius r carries a charge Q uniformly distributed over its length. A charge q is placed at its centre will experience a force equal to a) qQ 4πε 0 r 2 b) qQ 8πε 0 r 3 c) Zero d) None of these 26. Value of potential at a point due to a point charge is a) Inversely proportional to square of the distance b) Directly proportional to square of the distance c) Inversely proportional to the distance d) Directly proportional to the distance 27. The distance between a proton and electron both having a charge 1. 6×10 of a hydrogen atom −19 coulomb, is 10 The value of intensity of electric field produced on electron due to proton will be −10 metre. a) 2. 304×10 −10N/C b) 14. 4 V/m c) 16V/m d) 1. 44 × 10 11N/C 28. A capacitor of capacity C has charge Q and stored energy is W. If the charge is increased to 2Q, the stored energy will be a) 2W b) W/2 c) 4W d) W/4 29. The equivalent capacitance of three capacitors of capacitance C and are connected in parallel is 12 1 , C 2 C 3 units and product C unit. When the capacitors and are connected in parallel, the 1 . C 2 . C 3 = 48 C 1 C 2 equivalent capacitance is 6 units. Then the capacitances are a) 2, 3, 7 b) 1, 5, 2, 5, 8 c) 1, 5, 6 d) 4, 2, 6 30. A ball of mass 1 g and charge 10 moves from a point where potential is to the point where −8 C A. 600 volt B potential is zero. Velocity of the ball at the point B is 20 cm/s. The velocity of the ball at the point A will be a) 22. 8 cm/s b) 228 cm/s c) 16. 8 m/s d) 168 m/s 31. In the given circuit if point C is connected to the earth and a potential of + 2000 V is given to the point A, the potential at B is a) 1500 V b) 1000 V c) 500 V d) 400 V 32. When two identical capacitors are in series have 3μF capacitance and when parallel 12μF. What is the capacitance of each a) 6μ F b) 3μ F c) 12μ F d) 9μ F 33. At a certain distance from a point charge the electric field is 500 V/m and the potential is 3000 V. What is this distance Page| 4