*20 Figure 25-35 shows a variable "air gap" capacitor for manual tuning. Alternate plates are connected together; one group of plates is fixed in posi- tion, and the other group is capable of rotation. Consider a capacitor of n = 8 plates of al- ternating polarity, each plate having area A = 1.25 cm? and separated from adjacent plates by distance d = 3.40 mm. What is the maximum capacitance of the device? Figure 25-35 Problem 20.

Three capacitors are arranged as shown, if C₁ is a parallel plate capacitor d = 2 mm and cross-sectional area is 2 cm2, C₂ is a concentric spherical capacitor with R₁ = 1 mm and R₂ = 2 mm, and C₂ is a concentric cylindrical capacitor with R₁ = 1 mm , R₂ = 2 mm and length L=2 cm, determine: a. C₁, C₂, C3, and Cequivalent b. VAB, VBC C. Q₁, Q2, Qtotal. d. The energy of the capacitor

A slab of copper of thickness b = 1.68 mm is thrust into a parallel-plate capacitor of plate area A = 1.96 cm2 and plate separation d = 5.35 mm, as shown in the figure; the slab is exactly halfway between the plates. (a) What is the capacitance after the slab is introduced? (b) If a charge q = 2.68 µC is maintained on the plates, what is the ratio of the stored energy before to that after the slab is inserted? (c) How much work is done on the slab as it is inserted? (d) Is the slab sucked in or must it be pushed in? Copper (a) Number 4.73e-13 Units (b) Number i 0.686 (c) Number i 5.36e-10 Units J (d) sucked in

Kto A In the formula for capacitance C-- variable d represents: Select one: O separation between the plates of the capacitor O area of the metal plates that make up the capacitor for this experiment. O is the permittivity constant. O is the dielectric constant of the insulating material between the plates. When two capacitor plates are connected to a potential difference V, Select one: O None of the above One of the plates is charged with charge Q and the other plate is neutral. O The two plates are charged with equal but opposite amount of charge Q O The two plates are charged with equal amount of charge Q