The variable capacitance of an old radio tuner consists of four plates connected

Question

The variable capacitance of an old radio tuner consists of four plates connected together placed alternately between four other plates, also connected together (see the figure).(Figure 1) Each plate is separated from its neighbor by 1.7 mm of air. One set of plates can move so that the area of overlap of each plate varies from 1.2 cm2 to 9.8 cm2 .

Part A

Are these seven capacitors connected in series or in parallel?

Part B

Determine the range of capacitance values.

Express your answers using two significant figures separated by a comma.

Explanation / Answer

A. To decide about series or parallel we should see this from top view.

It shows that all positives are connected to other positive plates and all negatives are connected to other negative plates. which happens in parallel connection.

B. Cmin < C < Cmax

Amin = 1.2 cm^2 and Amax = 9.8 cm^2

Cmin = 4*eo*A/d = 4*8.85*10^-12*1.2*10^-4/(1.7*10^-3) = 2.49*10^-12

Cmin = 2.49 pF

Cmax = 4*eo*A/d = 4*8.85*10^-12*9.8*10^-4/(1.7*10^-3) = 20.4*10^-12

Cmax = 20.4 pF

2.49 pF < C < 20.4 pF

Let me know if you have any doubt.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.