Ssonastern gpnysits.commyct/itemview assignmentProblemiD-92190759 Ch 21 Electric

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Ssonastern gpnysits.commyct/itemview assignmentProblemiD-92190759 Ch 21 Electric Potential Problem 21.73 Part A Two 2.5-cm-diameter-disks spaced 20 mm apart form a parallel-plate capacitor. The electric field between the disks is 4 2x105 V/m What is the voltage across the capacitor? Express your answer with the appropriate units. Previous Answers Request Answer Incorrect; Try Again; 5 attempts remaining Part B How much charge is on each disk? Enter your answers numerically separated by a comma. Express your answers in coulombs

Explanation / Answer

Given diameter is 2.5 cm

radius r = 2.5 / 2 = 1.25 cm

r = 1.25 * 10^-2 m

Area of each plate A = pi * r^2

A = pi * (1.25 * 10^-2)^2

A = 4.9 * 10^-4 m^2

distance between the plates d = 2 mm = 2 * 10^-3 m

E = 4.2 * 10^5 V/m

part A

voltage V = E * d

V = 4.2 * 10^5 * 2 * 10^-3

V = 840 V

part B

capacitance C = €0 * A / d

C = (8.854 * 10^-12 * 4.9 * 10^-4) / (2 * 10^-3)

C = 2.17 * 10^-12 F

Charge on each plate Q = C * V

Q = 2.17 * 10^-12 * 840

Q = 1.82 nC

part C

initial speed    u = ?

final speed   v = 2.5 * 10^7 m/s

acceleration a = q*E / m

a = (1.6 * 10^-19 * 4.2 * 10^5) / (9.1 * 10^-31)

a = 7.38 * 10^16 m/s^2

distance s = 2 * 10^-3 m

from V^2 - u^2 = 2 * a * s

(2.5 * 10^7)^2 - u^2 = 2 * 7.38 * 10^16 * 2 * 10^-3

u = 1.81 * 10^7 m/s

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