Goals for Chapter 18

1. Goals for Chapter 18 • To calculate electrical potential energy. • To define potential. • To study equipotential surfaces • To review Millikan’s oil drop experiment. • To examine capacitors. • To determine electrical field energy

2. Electrical and gravitational forces - Figures 18.1-18.2 • The forces are similar and conservative.

3. Work and energy changes - Figures 18.3 • Work is done on the charge by the field.

4. Parallel plates and energy conservation – Example 18.2 • See the worked example on page 588 and Figure 18.8.

5. Potential of point and plate charges – Examples 18.3,4 • Refer to figures 18.9 and 18.10 with worked examples on pages 589-91.

6. The equipotential map around charges – Figure 18.11 • Around an charge or arrangement of charges regions of equal potential may be drawn as equal-potential lines.

7. Equipotential lines may not cross – Figure 18.12 • Considering conduction and geometry one may prove why the lines do not cross. • Refer to page 592 in your text.

8. Robert Millikan and electronic charge – Figure 18.16 He suspended charged oil drops of various masses between the parallel plates of a capacitor. His determination found many different multiple of *the same number*. The number was the charge of a single electron, 1.60217653(14)x10-19C.

9. Energetics of a single electron – Figure 18.17 One electron suspended in a 1V field allows the definition of an energy equivalence. 1eV = 1.602x10-19J

10. The capacitor – Figure 18.18 Devices may be constructed which separate two conductors of various sizes with materials of various conductance.

11. The symbol and units of capacitance – Figure 18.19 • Refer to pages 596 – 598 in your text. • Define the Farad and follow worked examples 18.6 and 18.7.

12. Capacitors are often joined – Figures 18.21 • Like resistors, capacitors may be combined sequentially (in series).

13. Capacitors are often joined II – Figures 18.22 • Like resistors, capacitors may be combined in simultaneous fashion (in parallel).

14. Capacitors store energy – Example 18.9 • This is the whine you can hear while an electronic flash charges. • Refer to the worked example on pages 602-603.

15. What is between the conductors? – Figures 18.26,27 • As we stated on an earlier slide, the amount of charge that may be stored in a capacitor depends in part on the “filler”.

16. Capacitors with different dialectrics – Figure 18.28 • Select the dialelectric from table 18.1.

17. Calculation with a specific dialectric – Example 18.10 Refer to the worked problem on page 605 and figure 18.29.