physics lab two question

LivePtpto Phpics Activity 30 Narne:

Date:

Wiring Capacitors in Series and Parallel

tn this assignment you will consider how to determine the effective capacitance when three different capacitors, labeled A, B, and C, are wired in series and when they are wired in parallel. Next you'll be asked to predict the capacitance of a nefwork ofthese capacitors that has both series and parallel elements in it. Finally, you'll examine a "movie" showing what happens to the effective capacitance when these three capacitors are combined in different ways.

Theoretical Relriew: [1] A capacitoris defined as any two Cspacltan@ iileter tnFI conducton an insulator where each conductor carries a net excess charge that is equal in magnitude and opposite in sig:r. Its capacitance, C, is defined as

c=9 tEq. ltv' ,,r here 0 is the magnirude of the excess charge on each plate and I'is rhe roitage (or potential difference) across the plate s,

-11 \l'e can use Gauss' Law to show that for an ideal parallei plate capacitor where the electric field lines are a1'* ar s perpendicular to the plates, the capacitance across ihe plates is related to the area, A, of the plates and spacing, d. betq'een them as shown in Equation 2,

, =ry tEq.2t rvhere K is the dielectric constant determined by the nature of the insulator between the conducting plates and ea is the electric constant (or permiaivity). j

1 . Preliminary Que stio ns

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Frgure 1: The capacitance of the capacitor network A, B & C is measured as 4.09 nano- Farads (nF). Capacitors B & G are wired in parallel, but this parallel combination is wired in series with capacitor A.

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qa\5# Note: You will receive full credit for each prediction you make in this preliminary section whether or not it matches conclusions you reach in the next section. As part of the learning process it is important for you to ictions witl outcomes. Do not change your Developing Hryntheses about how Capacitors Combine: In this section of the assignment you'll be using some reasoning based on the relationships shown in Equation 2 to predict how two identical capacitors ought to combine.

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30-1

Consider the diagram below. How might you calculate the ration? Ilints: If e, = 4. = A, what do you expect the

expect the

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to b€? Explain

2: Two capacitors iteareas At=fu-A

d1 =&=d

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