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6.3.2 Cylindrical capacitor
Lectures in General Physics
In the same way we can calculate the capacitance of cylindrical capacitor,
the result is as follow
C 2 πε l ο
ln
= (6.7)
( b a)
Where l is the length of the cylinder, a is the radius of the inside cylinder,
and b the radius of the outer shell cylinder.
6.3.3 Spherical Capacitor
In the same way we can calculate the capacitance of spherical capacitor, the
result is as follow
4πε ab
C = ο
(6.8)
b − a
Where a is the radius of the inside sphere, and b is the radius of the outer
shell sphere.
Example 6.2
An air-filled spherical capacitor is constructed with inner and outer
shell radii of 7 and 14cm, respectively. Calculate,
(a) The capacitance of the device,
(b) What potential difference between the spheres will result in a
charge of 4µC on each conductor?
(a)
Solution
−12
πε ab (4 × 8.85×
10 )(0.07)(0.14)
C = ο π
=
= 1.56 × 10
b − a
(0.14 − 0.07)
4 −11
F
(b) V
q
C
4×
10
1.56×
10
−6
= =
−11
= 2.56×
10
5
V
Dr. Hazem Falah Sakeek