1. Charges of +1.92 nC and -1.27 nC are located at opposite corners, A and C, re

Question

1. Charges of +1.92 nC and -1.27 nC are located at opposite corners, A and C, respectively, of a square which is L = 1.30 m on a side (as shown in the figure below ). What is the electric potential at a third corner, B, of the square (where there is no charge)?

2. A parallel plate capacitor is composed of two square plates, 10.0 cm on a side, separated by an air gap of 0.734 mm. It is initially charged to a 141-V potential difference. The plates are then physically separated by another 0.734 mm in such a way that none of the charge can leak off of the plates.

Find the new capacitance.

Find the new energy stored in the capacitor.

Explanation / Answer

1 ans

Given that

charge q1=1.92 nC

charge q2=-1.27 nC

now we find the electric potential at B

the electric potential =9*10^9[(1.92*10^-9/1.3)-(1.27*10^-9/1.3)]

=4.5 v

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2 ans

Given that

distance d=0.734 mm

length L=10 cm

area A=10^-2 m^2

potential difference V=141 V

now we find the capacitance

capacitance =8.85*10^-12*10^-2/0.734*10^-3

=12.1*10^-11 F

now we find the energy stored in capacitor

the energy stored U=1/2cv^2=1/2*12.1*10^-11*141^2=1.2*10^-6 J

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