announcements homework for tomorrow… ch. 29: probs. 20, 22, & 54 cq5: accelerates right cq6:...

Announcements Homework for tomorrow…

Ch. 29: Probs. 20, 22, & 54CQ5: accelerates rightCQ6: a) Va>Vb b) ΔVab<ΔVcd<ΔVef c) yes, no29.8: 1.5 V29.12: Ex(0cm<x<2cm) = +2,500 V/m Ex(2cm<x<3cm) = -10,000 V/m29.15: a) 27 V/m b) 3.7 V/m

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Chapter 29

Potential & Field(Combinations of Capacitors)

Kirchoff’s Loop Rule…

Conductors in Electrostatic Equilibrium…

Capacitance…

Review…

Any two electrodes, regardless of their shape, form a capacitor.

The capacitance of two electrodes is..

and depends only on the geometry of the electrodes.

Forming a Capacitor…

The spacing between the plates of a 1.0 μF capacitor is 0.050 mm

a. What is the surface area of the plates?

b. How much charge is on the plates if this capacitor is attached to a 1.5 V battery?

i.e. 29.6: Charging a capacitor

Consider two capacitors in parallel… Can we find an equivalent capacitor, Ceq, to the two

capacitors, C1 & C2?

Combinations of Capacitors

+

-

C1 C2

+

-

Ceq

Consider two capacitors in parallel… Can we find an equivalent capacitor, Ceq, to the two

capacitors, C1 & C2?

YES!

Combinations of Capacitors

+

-

C1 C2

+

-

Ceq

What about for several capacitors in parallel? Can we find an equivalent capacitor, Ceq, to the

capacitors, C1 , C2, … (all in parallel)?

Combinations of Capacitors

+

-

C1 C2

+

-

CeqC3

What about for several capacitors in parallel? Can we find an equivalent capacitor, Ceq, to the

capacitors, C1 , C2, … (all in parallel)?

YES!

Combinations of Capacitors

+

-

C1 C2

+

-

CeqC3

Consider two capacitors in series… Can we find an equivalent capacitor, Ceq, to the two

capacitors, C1 & C2?

Combinations of Capacitors

+

-

C1

C2

+

-

Ceq

Consider two capacitors in series… Can we find an equivalent capacitor, Ceq, to the two

capacitors, C1 & C2?

YES!

Combinations of Capacitors

+

-

C1

C2

+

-

Ceq

What about several capacitors in series? Can we find an equivalent capacitor, Ceq, to the

capacitors, C1 , C2 ,… (all in series)?

Combinations of Capacitors

+

-

C1

C2

+

-

Ceq

C3

What about several capacitors in series? Can we find an equivalent capacitor, Ceq, to the

capacitors, C1 , C2 ,… (all in series)?

YES!

Combinations of Capacitors

+

-

C1

C2

+

-

Ceq

C3

The equivalent capacitance is

1. 9 F.

2. 6 F.

3. 3 F.

4. 2 F.

5. 1/2 F.

Quiz Question 1

Find the charge on and the potential difference across each of the three capacitors in the figure below.

Given: E = 12 V, C1 = 3 μF, C2 = 5 μF , C3 = 1 μF

i.e. 29.7:A Capacitor Circuit

+

-

C1

C2 C3