Tiêu đề CAPACITOR.pdf ✅

NEET : Physics [ 160 ] www.allendigital.in  Digital CAPACITANCE, ENERGY STORED IN CAPACITOR & SPHERICAL CAPACITOR 1. The capacitance C of a capacitor is :- (1) independent of the charge and potential of the capacitor. (2) dependent on the charge and independent of potential. (3) independent of the geometrical configuration of the capacitor. (4) independent of the dielectric medium between the two conducting surfaces of the capacitor. 2. To increase the charge on the plate of a capacitor implies to :- (1) decrease the potential difference between the plates. (2) decrease the capacitance of the capacitor. (3) increase the capacitance of the capacitor. (4) increase the potential difference between the plates. 3. The net charge on a capacitor is :- (1) 2q (2) q/2 (3) 0 (4) infinity 4. The earth has Volume 'V' and Surface area 'A'; then its capacitance would be : (1) 0 A 4 V  (2) 0 V 4 A  (3) 0 V 12 A  (4) 0 A 12 V  5. Capacitors are used in electrical circuits where appliances need rapid : (1) Current (2) Voltage (3) Watt (4) Resistance 6. Which of the following is called electrical energy tank? (1) Resistor (2) Inductance (3) Capacitor (4) Motor 7. If the maximum circumference of a sphere is 2 m, then its capacitance in water would be :- (Dielectric constant of water = 81) (1) 27.65 pF (2) 2385 pF (3) 236.5 pF (4) 2865 pF 8. The two parallel plates of a condenser have been connected to a battery of 300 V and the charge collected at each plate is 1 C. The energy supplied by the battery is : (1) 6 × 10–4J (2) 3 × 10–4J (3) 1.5 × 10–4J (4) 4.5 × 10–4J 9. When a capacitor of value 200 F charged to 200V is discharged separately through resistance of 2 ohms and 8 ohms, then heat produced in joule will respectively be: (1) 4 and 16 (2) 16 and 4 (3) 4 and 8 (4) 4 and 4 10. The potential to which a conductor is raised, depends on :- (1) the amount of charge (2) the geometry and size of the conductor (3) both (1) and (2) (4) None of these 11. The charge q on a capacitor varies with voltage as shown in figure. The area of the triangle AOB represents : (1) electric field between the plates (2) electric flux between the plates (3) energy density (4) energy stored by the capacitor. 12. An uncharged capacitor is connected to a battery. On charging the capacitor :- (1) all the energy supplied is stored in the capacitor. (2) half the energy supplied is stored in the capacitor. (3) the energy stored depends upon the capacity of the capacitor only. (4) the energy stored depends upon the time for which the capacitor is charged. B A V O q Exercise - I
Capacitor  Digital www.allendigital.in [ 161 ] CYLINDRICAL CAPACITOR PARALLEL PLATE CAPACITOR & EFFECT OF DIELECTRIC SLAB 13. The capacity of parallel plate condenser depends on : (1) the type of metal used (2) the thickness of plates (3) the potential difference applied across the plates (4) the separation between the plates. 14. A parallel plate capacitor has rectangular plates of 400 cm2 area and are separated by a distance of 2 mm with air as the medium. What charge will appear on the plates if a 200 volt potential difference is applied across the capacitor? (1) 3.54 × 10–6 C (2) 3.54 × 10–8 C (3) 3.54 × 10–10 C (4) 1770.8 × 10–13 C 15. There are two metallic plates of a parallel plate capacitor. One plate is given a charge +q while the other is earthed as shown. Points P, P1 and P2 are taken as shown in adjoining figure. Then the electric intensity is not zero at : (1) P only (2) P1 only (3) P2 only (4) P, P1 and P2 16. The distance between the plates of a circular parallel plate capacitor of diameter 40 mm, whose capacity is equal to that of a metallic sphere of radius 1m will be : (1) 0.01 mm (2) 0.1 mm (3) 1.0 mm (4) 10 mm 17. The energy density in a parallel plate capacitor is given as 2.1 × 10–9 J/m3. The value of the electric field in the region between the plates is : (1) 2.1 NC–1 (2) 21.6 NC–1 (3) 72 NC–1 (4) 8.4 NC–1 18. A charged parallel plate capacitor of distance (d) has U0 energy. A slab of dielectric constant (K) and thickness (d) is then introduced between the plates of the capacitor. The new energy of the system is given by : (1) KU0 (2) K2U0 (3) U0 K (4) 0 2 U K 19. The energy and capacity of a charged parallel plate capacitor are U and C respectively. Now a dielectric slab of r = 6 is inserted in it then energy and capacity becomes : (Assuming charge on plates remains constant) (1) 6U, 6C (2) U, C (3) U 6 , 6C (4) U, 6C 20. Distance between the plates of a parallel plate capacitor is 'd' and area of each plate is A. When a slab of dielectric constant K and thickness t is placed between the plates, its capacity becomes: (1) 0 A 1 d t 1 K        + −       (2) 0A 1 d t 1 K        + +       (3) 0A 1 d t 1 K        − +       (4) 0A 1 d t 1 K        − −       21. When a slab of dielectric medium is placed between the plates of a parallel plate capacitor which is connected with a battery, then the charge on plates in comparision with earlier charge : (1) is less (2) is same (3) is more (4) depends on the nature of the material inserted 22. A glass slab is put within the plates of a charged parallel plate condenser. Which of the following quantities does not change? (1) energy of the condenser (2) capacity (3) intensity of electric field (4) charge 23. A parallel plate capacitor is connected to a battery and a dielectric slab is inserted between the plates, then which quantity increase : (1) potential difference (2) electric field (3) stored energy (4) E.M.F. of battery P2 P P1
NEET : Physics [ 162 ] www.allendigital.in  Digital 24. A parallel plate capacitor is charged by a battery. After charging the capacitor, battery is disconnected and a dielectric plate is inserted between the plates. Then which of the following statements is not correct there is a/an? (1) increase in the stored energy (2) decrease in the potential difference (3) decrease in the electric field (4) increase in the capacitance 25. A parallel plate capacitor is charged by a battery. After charging the capacitor, battery is disconnected and distance between the plates is decreased then which of the following statement is correct? (1) electric field does not remain constant (2) potential difference is increased (3) the capacitance decreases (4) the stored energy decreases 26. A parallel plate capacitor is connected with a battery whose potential difference remains constant. If the plates of the capacitor are shifted apart then the intensity of electric field : (1) decreases and charge on plates also decreases. (2) remains constant but charge on plates decreases. (3) remains constant but charge on the plates increases. (4) increases but charge on the plates decreases. 27. A parallel plate capacitor is charged with a battery and afterwards the battery is removed. if now, with the help of insulating handles, the distance between the plates is increased, then (1) charge on capacitor increases and capacity decreases. (2) potential difference between the plates increases. (3) capacity of capacitor increases. (4) value of energy stored in capacitor decreases. 28. Can a metal be used as a medium for dielectric? (1) Yes (2) No (3) Depends on its shape (4) Depends on dielectric 29. A parallel plate air capacitor has a capacitance C. When it is half filled with a dielectric of dielectric constant 5, the percentage increase in the capacitance will be :- (1) 400% (2) 66.6% (3) 33.3% (4) 200% COMBINATION OF CAPACITORS & SHARING OF CHARGES 30. The equivalent capacitance between the points A and B in the given diagram is : (1) 8 F (2) 6 F (3) 8 F 3  (4) 3 F 8  31. In an adjoining figure three capacitors C1, C2 and C3 are joined to a battery. The correct condition will be : (1) Q1 = Q2 = Q3 and V1 = V2 = V3 = V (2) Q1 = Q2 + Q3 and V = V1+ V2 + V3 (3) Q1 = Q2 + Q3 and V = V1 + V2 (4) Q2 = Q3 and V2 = V3 (Symbols have their usual meanings) 32. A number of capacitors, each of capacitance 1 F and each one of which gets punctured if a potential difference just exceeding 500 volt is applied, are provided. Then an arrangement suitable for giving a capacitor of capacitance 3 F across which 2000 volt may be applied requires at least : (1) 4 component capacitors (2) 12 component capacitors (3) 48 component capacitors (4) 16 component capacitors d 2F 2F 2F 2F A B V V1C1Q1 V2C2Q2 V3C3Q3
Capacitor  Digital www.allendigital.in [ 163 ] 33. The effective capacity of the network between terminals A and B is : (1) 6 μF (2) 20 μF (3) 3 μF (4) 10 μF 34. A series combination of two capacitances of value 0.1 F and 1F is connected with a source of voltage 500 volts. The potential difference in volts across the capacitor of value 0.1 F will be: (1) 50 (2) 500 (3) 45.5 (4) 454.5 35. The value of equivalent capacitance of the combination shown in figure, between the points P and Q is : (1) 3C (2) 2C (3) C (4) C/3 36. The equivalent capacitance between points A and B of the circuit shown will be : (1) 2 3 F (2) 5 3 F (3) 8 3 F (4) 7 3 F 37. The effective capacitance between the points P and Q of the arrangement shown in the figure is: (1) (1/2) F (2)1 F (3) 2 F (4) 1.33 F 38. Two spheres of radii R1 and R2 having equal charges are joined together with a copper wire. If V is the potential of each sphere after they are separated from each other, then the initial charge on both spheres was : (1) ( 1 2 ) V R R k + (2) ( 1 2 ) V R R 2k + (3) ( 1 2 ) V R R 3k + (4) ( ) ( ) 1 2 1 2 V R R k R R+ 39. Two spheres of radii 1 cm and 2 cm have been charged with 1.5 × 10–8 and 0.3 × 10–7 coulombs of positive charge. When they are connected with a wire, charge : (1) will flow from the first to the second (2) will flow from the second to the first (3) will not flow at all (4) may flow either from first to second, or from the second to first, depending upon the length of the connecting wire 40. Half of the space between a parallel plate capacitor is filled with a medium of dielectric constant K parallel to the plates. If initially the capacity was C, then the new capacity will be : (1) 2KC/(1+K) (2) C (K+1)/2 (3) CK/(1+K) (4) KC 41. Two capacitances C1 and C2 in a circuit are joined as shown in figure The potential of point A is V1 and that of B is V2. The potential of point D will be : (1) 1 2 (V1+V2) (2) 2 1 1 2 1 2 C V C V C C + + (3) 1 1 2 2 1 2 C V C V C C + + (4) 2 1 1 2 1 2 C V C V C C − + 42. A circuit has a section AB as shown in the figure with E = 10 V, C1 = 1.0 F, C2 = 2.0 F and the potential difference VA–VB = 5 V. The voltage across C1 is : (1) Zero (2) 5 V (3) 10 V (4) 15 V 6F 6F 6F 6F A B 20F 2C 2C C 2C C C P Q A B 1F 1F 2F 1F 2F 2F 5F 2F 2F 1F 1F P Q V C1 C2 1 A D B V2 E A C1 C2 B