Question

Two 5.5 mm × 5.5 mm electrodes are held 0.10 mm apart and are attached to 8.5 V battery. Without disconnecting the battery, a 0.10-mm-thicksheet of Mylar is inserted between the electrodes.

a) What is the capacitor's charge before the Mylar is inserted?

b) What is the capacitor's potential difference after the Mylar is inserted?

c) What is the capacitor's electric field after the Mylar is inserted?

d) What is the capacitor's charge after the Mylar is inserted?

Answer 1

a)

C = 8.85* 10^-12* (5.5* 10^-3)^2/ ( 0.1* 10^-3) = 2.677* 10^-12 F

charge

q = CV = 2.276* 10^-11 C

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b)

V = 8.5 V

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c)

new charge

Q = kCV = 3.1* 2.276* 10^-11 = 7.056* 10^-11 C

field betweenthe plates

E = Q/ ( A eo)

E = 7.056* 10^-11 / ( 5.5* 10^-3* 5.5* 10^-3* 8.85* 10^-12)

E = 2. 636* 10^5 N/C

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d)

Q = 7.056* 10^-11 C

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