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Capacitor || Physics || B.Optom
This document discusses parallel plate capacitors and capacitor basics. It defines the capacitance of a parallel plate capacitor and explains how capacitance is affected by changing the plate area, distance between plates, and inserting a dielectric material. It also covers energy stored in a capacitor, electric field and potential, equipotential surfaces, and static electricity examples. Key points covered include the formula for capacitor capacitance and energy storage, and that capacitance increases when the plate area or dielectric constant increases but decreases when the distance between plates increases.
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Capacitor || Physics || B.Optom
- 1.
- 2. PARALLEL PLATE CAPACITOR C= 𝐾𝜖0𝐴 𝑑
- 3. 1) The capacitanceof a capacitor is independent of a) Quality of plates b) Size of plates c) Distance between the plates d) Medium between plates Ans: a 2) If the distance between the plates of parallel plate capacitor is doubled, capacitance becomes a) Halved b) Doubled c) Does not change d) None of above Ans: a
- 4. 3) If thearea of parallel plate capacitor is doubled, the capacitance becomes a) Doubled b) Halved c) Does not change d) None of above Ans: a 4) If the area between parallel plate capacitor and the distance between them is doubled, the new capacitance becomes a) Doubled b) Halved c) Does not change d) None of above Ans: c
- 5. 5) A glassslab of uniform thickness is introduced between the plates of a parallel plate capacitor. The capacity of capacitor a) Increase b) Decrease c) Remains same d) Become infinite Ans: a 6) The capacitance of parallel plate capacitor is C. If a medium of dielectric constant 3 is inserted between the plates, then capacitance becomes a) C b) 2C c) 3C d) 4C Ans: b
- 6. ENERGY STORED INCAPACITOR E = ½ CV2 Energy is stored in the form of electric field
- 7. 1) Energy storedin capacitor is in the form of a) Electric field b) Magnetic field c) Both electric and magnetic field d) None of above Ans: a 2) Energy stored in inductor is in the form of a) Electric field b) Magnetic field c) Both electric and magnetic field d) None of above Ans: b
- 8. Energy density =½ 𝜖0E2
- 9. 1) Energy densityin capacitor is denoted by a) ½ 𝜖0E2 b) 𝜖0E2 c) ½ E2 d) ½ 𝜖0E Ans: a
- 10. If ‘n’ dropsof radius ‘r’ and charge ‘q’ are joined to form bigger drop then a) Radius of big drop, R = n 1/3 r b) Total charge on big drop Q = nq c) Total capacitance = n 1/3 C d) Total potential = n 2/3 V
- 11. 1) 8 equaldrops of radius r are coalesced to form a bigger drop. Capacitance of bigger drop is a) 2C b) 3C c) 4C d) 5C Ans: a 2) 8 equal drops of radius r and voltage V are coalesced to form a bigger drop. Voltage of bigger drop is a) 2V b) 3V c) 4V d) 5V Ans: c
- 12. 3) If potentialof one small drop is V and n such identical drops coalesce together then final potential of larger drop is a) n 1/3 V b) n 2/3 V c) n 4/3 V d) n V Ans: b
- 13. 1) In acharged capacitor the energy resides a) On the positive plate b) On both positive and negative plates c) in the field between the plates d) Around the edge of capacitor plates Ans: c 2) The capacitance of earth is a) 712𝜇𝐹 b) 71𝜇𝐹 c) 72𝜇𝐹 d) 7𝜇𝐹 Ans: a
- 14. ELECTRIC FIELD ANDPOTENTIAL
- 15. E = 𝐹 𝑞 V = 𝑊 𝑞 E= 𝑉 𝑑
- 16. 1) When 1Ccharge is moved form A to B at the potential of 2V then work done in doing so is a) 1J b) 2J c) 5J d) 10J Ans: b 2) If the electric field intensity is 106 V/m. then find the distance between the plates kept at a potential difference of 103V a) 10-3 b) 109 c) 1015 d) 1039 Ans: a
- 17. EQUIPOTENTIAL SURFACE Surface havingequal potential So potential difference is zero V = 𝑊 𝑞 So work done is equipotential surface is zero
- 18. 1) Work doneon equipotential surface is a) Zero b) Positive c) Negative d) Cannot be said Ans: a
- 19.
- 20. 1) A thinstream of water from a tap is attracted by placing a rod near it the rod is a) The south pole of magnet b) Charged with static electricity c) The north pole of magnet d) Any non magnetic substance Ans: b 2) When a woolen sweater worn over a nylon shirt is removed, sparking is observed due to a) Static electricity b) Friction c) Dynamic electricity d) None of above Ans: a
- 21. 3) Vann degraff generator produces a) Static electricity b) Friction c) Dynamic electricity d) None of above Ans: a
- 22. 1) Force betweentwo charges 1𝜇𝐶 𝑒𝑎𝑐ℎ 𝑠𝑒𝑝𝑎𝑟𝑎𝑡𝑒𝑑 𝑏𝑦 1𝑚 𝑖𝑠 a) 9 x 10-4 N b) 9 x 10-3 N c) 9 x 10-5 N d) 9 x 10-2 N Ans: b 2) What is the force of attraction between electron and proton separated by 0.53A0 a) 8.2 x 10-6 N b) 8.2 x 10-4 N c) 8.2 x 10-5 N d) 8.2 x 10-3 N Ans: a
- 23. 3) If asoap bubble is give small positive or negative charge, its radius a) Increases b) Decreases c) Does not change d) None of above Ans: a
- 24.