Page 1 1 CAPACITOR 2CA-01 Conceptual and NCERT Level 1. Suppose the two plates of a capacitor have different areas. When the capacitor is charged by connecting it to a battery, do the charges on the two plates have equal magnitude, or may they be different? Explain your reasoning. 2. The charged plates of a capacitor attract each other, so to pull the plates farther apart requires work by some external force. What becomes of the energy added by this work ? Explain your reasoning. 3. The two plates of a capacitor are given charges ±Q. The capacitor is then disconnected from the charging device so that the charges on the plates can’t change, and the capacitor is immersed in a tank of oil. Does the electric field between the plates increase, decrease or stay the same ? Explain your reasoning. How can this field be measured ? 4. At which of the two points, 1 or 2, of a charged capacitor with nonparallel plates is the surface charge density greater ? 5. In the figure shown, the plate A has 100µ charge, while the plate B has 60 µC charge. (a) When both switches are open, then q 1 = _____________ q 2 = _____________ q 3 = _____________ q 4 = _____________ (b) When switch S 1 is closed only then q 1 = ____________ q 2 = _____________ q 3 = ____________ q 4 = _____________ (c) When switch S 2 is also closed, then q 1 = ____________ q 2 = _____________ q 3 = ____________ q 4 = _____________ 6. A capacitor of capacitance C is charged to a potential difference V from a cell and then disconnected from it. A charge +Q is now given to its positive plate. Find the potential difference across the capacitor. 7. A parallel-plate vacuum capacitor with plate area A and separation x has charges +Q and - Q on its plates. The capacitor is disconnected from the source of charge, so the charge on each plate remains fixed. (a) What is the total energy stored in the capacitor ? (b) The plates are pulled apart an additional distance dx. What is the change in the stored energy? (c) If F is the force with which the plates attract each other, then the change in the stored energy must equal the work dW = F dx done in pulling the plates apart. Find an expression for F. (d) Explain why F is not equal to QE, where E is the electric field between the plates. 8. (a) How many excess electrons must be added to one plate and removed from the other to give a 5.00 nF parallel plate capacitor 25.0 J of stored energy? (b) How could you modify the geometry of this capacitor to get it to store 50.0 J of energy without changing the charge on its plates? 9. A capacitor is connected across a battery. (a) Why does each plate receive a charge of exactly the same magnitude? (b) Is this true even if the plates are of different size? (Yes/No) + 2 1 ? s 1 q 1 q 2 A s 2 q 3 q 4 B Page 2 1 CAPACITOR 2CA-01 Conceptual and NCERT Level 1. Suppose the two plates of a capacitor have different areas. When the capacitor is charged by connecting it to a battery, do the charges on the two plates have equal magnitude, or may they be different? Explain your reasoning. 2. The charged plates of a capacitor attract each other, so to pull the plates farther apart requires work by some external force. What becomes of the energy added by this work ? Explain your reasoning. 3. The two plates of a capacitor are given charges ±Q. The capacitor is then disconnected from the charging device so that the charges on the plates can’t change, and the capacitor is immersed in a tank of oil. Does the electric field between the plates increase, decrease or stay the same ? Explain your reasoning. How can this field be measured ? 4. At which of the two points, 1 or 2, of a charged capacitor with nonparallel plates is the surface charge density greater ? 5. In the figure shown, the plate A has 100µ charge, while the plate B has 60 µC charge. (a) When both switches are open, then q 1 = _____________ q 2 = _____________ q 3 = _____________ q 4 = _____________ (b) When switch S 1 is closed only then q 1 = ____________ q 2 = _____________ q 3 = ____________ q 4 = _____________ (c) When switch S 2 is also closed, then q 1 = ____________ q 2 = _____________ q 3 = ____________ q 4 = _____________ 6. A capacitor of capacitance C is charged to a potential difference V from a cell and then disconnected from it. A charge +Q is now given to its positive plate. Find the potential difference across the capacitor. 7. A parallel-plate vacuum capacitor with plate area A and separation x has charges +Q and - Q on its plates. The capacitor is disconnected from the source of charge, so the charge on each plate remains fixed. (a) What is the total energy stored in the capacitor ? (b) The plates are pulled apart an additional distance dx. What is the change in the stored energy? (c) If F is the force with which the plates attract each other, then the change in the stored energy must equal the work dW = F dx done in pulling the plates apart. Find an expression for F. (d) Explain why F is not equal to QE, where E is the electric field between the plates. 8. (a) How many excess electrons must be added to one plate and removed from the other to give a 5.00 nF parallel plate capacitor 25.0 J of stored energy? (b) How could you modify the geometry of this capacitor to get it to store 50.0 J of energy without changing the charge on its plates? 9. A capacitor is connected across a battery. (a) Why does each plate receive a charge of exactly the same magnitude? (b) Is this true even if the plates are of different size? (Yes/No) + 2 1 ? s 1 q 1 q 2 A s 2 q 3 q 4 B 2 2CA-01 CAPACITOR Conceptual and NCERT Level 10. The plates of a plane capacitor are drawn apart keeping them connected to a battery. Next the same plates are drawn apart from the same initial condition keeping battery disconnected. In which case is more work done ? 11. If a small charge q is moved along a closed path in the field between the plates of a parallel - plate capacitor, will any work be done by the agent who moves the charge? (Yes / No) 12. Which of the following changes to an ideal parallel - plate capacitor connected to an ideal battery will result in an increase in the charge on the capacitor ? (a) Decreasing the potential difference across the plates (b) Decreasing the area of the plates (c) Decreasing the separation of the plates 13. A parallel - plate capacitor is connected to an ideal battery, which provides a fixed potential difference. Originally the energy stored in the capacitor is U 0 . If the distance between the plates is doubled, then the new energy stored in the capacitor will be…….. 14. A capacitor has square plates of side a making an angle q with each other as shown in figure. Show that the capacitance of this arrangement is given by 2 0 1, 2 a a C tt ? ? ?? ?? ?? ?? where d is the minimum separation between the plates at one end. q is very small. 15. Each plate of a parallel plate air capacitor has area S = 5 × 10 -3 m 2 and are d = 8.80 mm apart. Plate A has positive change q 1 = +10 -10 C and plate B and change q 2 = +2 × 10 -10 C. Calculate the energy supplied by a battery of emf E = 10V When its positive terminal is connected to plate A and negative terminal to plate B. (Given ? 0 = 8.8 × 10 -12 ) 16. A circuit has a section AB shown in figure. 5V A B C 1 =1 F ? C 2 =2 F ? 10V The emf of the cell is 10 V and the capacitors have capacitances C 1 = 1µF and C 2 = 2µF. The potential difference V AB = 5V. Find the charges on the capacitors. 17. Four identical capacitor plates, each of area A, are arranged such that adjacent plates are a distance d apart. The plates are connected to a source of emf V as shown in the figure. Find the charge on plate 1 and that on Plate 4. 18. N identical capacitors are connected in parallel and then a potential difference of V is applied to them. The potential difference when these capacitors are reconnected in series, their charges being left undisturbed ? 19. In the arrangement shown, plate A & C are connected together by a conducting wire & plate B is given a charge equal to 60 µC. The ratio d 1 / d 2 = 2. q 1 = __________________ q 2 = __________________ q 3 = __________________ q 4 = __________________ q 5 = __________________ q 6 = __________________ ? a a t + V 1 2 3 4 5 A B C q 1 q 2 q 3 q 4 q 5 d 1 d 2Read More

Offer running on EduRev: __Apply code STAYHOME200__ to get INR 200 off on our premium plan EduRev Infinity!