A cylindrical capacitor is constructed using two coaxial cylinders of the same length 10 cm and of radii 2 mm and 4 mm.

a) Calculate the capacitance.


b) Another capacitor of the same length is constructed with cylinders of radii 4 mm and 8 mm. Calculate the capacitance.


Given


Length, l = 10cm


Radius, R1 = 2mm


Radius, R2 = 4mm



Formula used :


a) The capacitance of the cylindrical capacitor is given by



Where


l length of the cylinder


R2 radius of outer cylinder


R1 radius of inner cylinder permittivity of the free space


ε₀ permittivity of the free space = ε₀=


Putting the value in the above formula, we get



b) Another cylindrical capacitor of same but different radius R1=4mm and R2= 8mm


If we compare the radii in a) with b), they give the same ratio




So capacitance is also same as a) is



Capacitance of cylindrical capacitor for both a) and b) is same and is =8pF


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