A capacitor is constructed from two copper plates, each measuring 1 mm times 2.5
ID: 2061618 • Letter: A
Question
A capacitor is constructed from two copper plates, each measuring 1 mm times 2.5 mm and 155 mu m thick. The two plates are placed such that they face each other and are separated by a 1 mu m gap. Calculate the resulting capacitance if (a) the intervening dielectric has a permittivity of l.35 epsilon 0. (b) the intervening dielectric has a permittivity of 3.5 epsilon 0; (c) the plate separation is increased by 3.5 mu m and the gap is filled with air. (d) the plate area is doubled and the 1 mu m gap is filled with air.Explanation / Answer
Capacitance is given as:
C=A/d
A=1*10^-3*2.5*10^-3 =2.5*10^-6
d=1*10^-6 m
(1) C=1.35*8.54*10^-12*2.5*10^-6/1*10^-6
=2.88225*10^-11 F
(2)
C=3.5*8.54*10^-12*2.5*10^-6/1*10^-6
=7.4725*10^-11 F
(3)
d=3.5+1=4.5*10^-6
C=8.54*10^-12*2.5*10^-6/4.5*10^-6
=4.7444*10^-12 F
(4)
A=2*2.5*10^-6
d=1*10^-6 m
C=8.54*10^-12*2*2.5*10^-6/1*10^-6
=4.27*10^-11 F
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