Dielectrics 11/10/08

Figure 26. 8 Circuit symbols for capacitors, batteries, and switches Figure 26.8 Circuit symbols for capacitors, batteries, and switches. Note that capacitors are in blue and batteries and switches are in red. Fig 26-8, p.802

Active Figure 26.9 (a) A parallel combination of two capacitors in an electric circuit in which the potential difference across the battery terminals is V.

Active Figure 26.9 (a) A parallel combination of two capacitors in an electric circuit in which the potential difference across the battery terminals is V. (b) The circuit diagram for the parallel combination. (c) The equivalent capacitance is Ceq C1=C2. Fig 26-9, p.803

Active Figure 26. 10 (a) A series combination of two capacitors Active Figure 26.10 (a) A series combination of two capacitors. The charges on the two capacitors are the same. Fig 26-10a, p.804

Active Figure 26.10 (b) The circuit diagram for the series combination. Fig 26-10b, p.804

Active Figure 26. 10 (a) A series combination of two capacitors Active Figure 26.10 (a) A series combination of two capacitors. The charges on the two capacitors are the same. (b) The circuit diagram for the series combination. (c) The equivalent capacitance can be calculated from the relationship 1 /Ceq =1 /C 1+ 1/ C 2 . Fig 26-10, p.804

Active Figure 26.9 (b) The circuit diagram for the parallel combination. Fig 26-9b, p.803

Active Figure 26.9 (c) The equivalent capacitance is Ceq C1=C2. Fig 26-9c, p.803

O on the negative charge is also of magnitude Fa sin ; here again, the force tends to Figure 26.22 An electric dipole in a uniform external electric field. The dipole moment p is at an angle to the field, causing the dipole to experience a torque. Fig 26-22, p.815

Figure 26.25 (a) Polar molecules are randomly oriented in the absence of an external electric field. Fig 26-25a, p.817

Figure 26.25 (b) When an external electric field is applied, the molecules partially align with the field. Fig 26-25b, p.817

that the induced charge density is two-thirds the charge density on the plates. If no dielectric is present, then 1 and ind 0 as expected. However, if the dielectric is replaced by an electrical conductor, for which E 0, then Equation 26.22 indicates Figure 26.26 Induced charge on a dielectric placed between the plates of a charged capacitor. Note that the induced charge density on the dielectric is less than the charge density on the plates. Fig 26-26, p.818

E0 = /0 Eind = -ind/0 ET = E0 + Eind Fig 26-25c, p.817 Figure 26.25 (c) The charged edges of the dielectric can be modeled as an additional pair of parallel plates establishing an electric field Eind in the direction opposite to that of E0. Fig 26-25c, p.817

II. Description input light write light (zero intensity) phase-shifted light (no phase shift) write light input light (nonzero intensity) phase-shifted light Not all the molecules will point in the same direction. The average direction of orientation is called the “director.” The device works in reflections and behaves like a deformable mirror. Amorphous Silicon Liquid Crystal