Tiêu đề 16. Electric Charges And Fields.pdf ✅

1. Force between A and B is F. If 75% charge of A is transferred to B then force between A and B is : (1) 4 F (2) 4F (3) F (4) None 2. A semi circular arc of radius a is charged uniformly and the charge per unit length is . The electric field at the centre is :- 3. Four charges equal to –Q are placed at the four corners of a square and a charge q is at its centre. If the system is in equilibrium, the value of q is:- 4. The force on a charge situated on the axis of a small dipole is F. If the charge is shifted to double the distance, the acting force will be - (1) 4F (2) F/2 (3) F/4 (4) F/8 5. A and B are concentric conducting spherical shells. A is given a positive charge while B is earthed. Then- (1) A and B both will have the same charge densities (2) the potential inside A and outside B will zero (3) the electric field between A and B is non zero (4) the electric field inside A and outside B is non zero. 6. The ratio of electric flux through surfaces S1and S2 is: (1) 1 : 1 (2) –3 : 1 (3) 3 : 1 (4) –1 : 3 7. Two point charges Qa & Qb, whose magnitudes are same are positioned at a certain distance from each other with Qa at origin. Graph is drawn between electric field strength at points between Qa&Qb and distance x from Qa. E is taken positive if it is along the line joining from Qa to Qb. From the graph, it can be decided that (1) a is positive, b is negative (2) a and b both are positive (3) a and b both are negative (4) a is negative, b is positive 8. A charge q is placed at the centre of the cubical vessel (with one face open) as shown in figure. The flux of the electric field through the surface of the vessel is 9. Two metal spheres, one of radius R and the other of radius 2R, both have same surface charge density . If they are brought in contact and separated, then the new surface charge densities on each of the sphere are respectively:- 10. Two identical small balls, each of mass m and charge q are suspended by two light inelastic on-conducting threads each of Electric Charges and Fields
length from the same fixed point support. If the distance d between two balls is very less, then d is equal to- 11. A small metal ball is suspended in a uniform electric field with the help of an insulated thread. If a high energy x-ray beam falls on the ball, then the ball :- (1) will be deflected in the direction of the field (2) will be deflected in the direction opposite to the field (3) will not be deflected (4) will oscillate in the field 12. A point charge q is placed in a cavity in a metal block. If a charge Q is brought outside the metal, then the electric force experienced by q is:- (1) Proportional to Q (2) Proportional to (Q-q) (3) Zero (4) Cannot be determined 13. Six charges are placed at the vertices of a regular hexagon as shown in the figure. The electric field on the line passing through point O and perpendicular to the plane of the figure at a distance of x(>> a) from O is :- 14. A given charge situated at a distance r from an electric dipole on it axis experiences a force F. If the distance of the charge from the dipole is doubled, the force acting on the charge will be:- (1) 4F (2) F/2 (3) F/4 (4) F/8 15. Three charges are arranged along a straight line as shown in the figure. Calculate the total electric field intensity due to all three charges at the point P:- (1) Zero (2) 8.48 × 103 N/C (3) 16.43 × 103 N/C (4) 5.3 × 103 N/C 16. Four charges are placed at the circumference of a dial clock as shown in figure. If the clock has only hour hand, then the resultant force on a charge q0 placed at the centre, points in the direction which shows the time as:– (1) 1:30 (2) 7:30 (3) 4:30 (4) 10:30 17. A wheel having mass m has charge +q and –q on diametrically opposite points. It remains in equilibrium on a rough inclined plane in the presence of uniform vertical electric field E equal to :- (–q is in contact with the incline plane) 18. A soap bubble is charged its size : (1) will decrease (2) will remain same (3) Will increase (4) before increase after decrease 19. In given diagram. Find distance of neutral point from particle of charge e is :-
(1) 20 cm (2) 10 cm (3) 15 cm (4) 7.5 cm 20. Find change in mass of a body if it is given +2C charge. 21. Similar charges are placed at corners of a square and a charge q0 is placed at it's centre find net force on it :- 22. A thin square plate is placed in x-y plane as shown in fig. such that is centre coinsides with origine it's charge density at point (x, y) is  = 0 xy(where 0 is constant). Find total charge on the plate. 23. Two parallel metal plates having charges + Q and – Q face each other at a certain distance between them. If the plates are now dipped in kerosene oil tank, the electric field between the plates will :- (1) Increase (2) Decrease (3) Remain same (4) Become zero 24. Two spheres of radius R & 2R having charge Q& 2Q respectively are placed far away from each other. How much charge will flow when key 'k' is pressed? (1) Q (2) 2 Q (3) 3 Q (4) Zero 25. Two point charges of + 2  C and +  C repel each other with a force of 12 N. If each is given an additional charge of – 4  C, then force will become :– (1) 4N (attractive) (2) 60 N (attractive) (3) 4 N (Repulsive) (4) 12 N (attractive) 26. A semicircular ring of radius 'a' has charge density 0    = cos where 0 is constant and ‘ ’ is shown in figure. Then total charge on the ring is :- (1) 0 2 R (2) 0 4 R (3) 0 3  R (4) zero 27. Two concentric spherical shells of radius R1& R2have q1& q2 charge respectively as shown in figure. How much charge will flow through key k when it is closed :- (1) 1 2 2 2 R R q R   +     (2) 1 1 2 2 2 q R q R R + (3) 2 1 2 2 R R q R   −     (4) 2 2 2 1 2 q R q R R −
28. Two concentric spheres A & B are kept very near to each other. A is negatively charged and B is earthed. The true statement is :- (A) Charge on B is zero (B) Potential at B is zero (C) Charge is uniformly distributed on A (D) Charge is non uniformly distributed on A (1) A & C (2) A & D (3) B & C (4) B & D 29. Electric field at the centre 'O' of a semicircle of radius 'a' having linear charge density  is givenas (1) 0 2 a   (2) 0 a   (3) 0 2 a    (4) 0 a    30. A charge q is placed at corner of a closed cube the flux related with any face of cube. (1) Must be 0 8 q  (2) May be 0 q  (3) Must be zero (4) May be zero 31. An electron travels a distance of 0.10 m in an electric field of intensity 3200 V/m, enters perpendicular to the field with a velocity 7 4 10  m/s, what is its deviation in its path : (1) 1.76 mm. (2) 17.6 mm. (3) 176 mm. (4) 0.176 mm. 32. A point charge 'q' is placed at centre of hollow cylinder as shown in figure if this charge is moved towards face 'A' then electric flux related with face'B' will (1) increase (2) decrease (3) will remain same (4) become zero 33. The electric field at a distance 3 2 R from the centre of a charged conducting spherical shell of radius R is E. The electric field at a distance 2 R from the centre of the sphere is :- (1) E (2) 2 E (3) 3 E (4) Zero 34. Electric dipole is placed in front of a fixed point charge 'Q' then :- (1) Force must be zero (2) Torque must be non zero (3) Force must be non zero (4) Both may be non zero 35. Two identical metal sphere carry charges of +q and –2q respectively. When the sphere are separated by a large distance r, the force between them is F. Now the spheres are allowed to touch and then moved back to same separation. Find the new force of repulsion between them. (1) F/4 (2) F/8 (3) F/2 (4) None of these