Chapter 23 Electrostatic Energy and Capacitors

1) The charge on the square plates of a parallel-plate capacitor is Q. The potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. The amount of charge on the plates is now equal to A) 4Q. B) 2Q. C) Q. D) Q/2. E) Q/4. Answer: D Var: 1 2) The electric field between square the plates of a parallel-plate capacitor has magnitude E. The potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. The magnitude of the electric field between the plates is now equal to A) 4E. B) 2E. C) E. D) E/2. E) E/4. Answer: D Var: 1 3) Equal but opposite charges Q are placed on the square plates of an air-filled parallel-plate capacitor. The plates are then pulled apart to twice their original separation, which is small compared to the dimensions of the plates. Which of the following statements about this capacitor are true? (There may be more than one correct choice.) A) The energy stored in the capacitor has doubled. B) The energy density in the capacitor has increased. C) The electric field between the plates has increased. D) The potential difference across the plates has doubled. E) The capacitance has doubled. Answer: A, D Var: 1 4) When two or more capacitors are connected in series across a potential difference A) the potential difference across the combination is the algebraic sum of the potential differences across the individual capacitors. B) each capacitor carries the same amount of charge. C) the equivalent capacitance of the combination is less than the capacitance of any of the capacitors. D) All of the above choices are correct.