two circular metal plates each of radius 10 cm are kept parallel to each other at a distance of 1 mm. what kind of capacitor do they make? mention one application of this capacitor. if the radius of each of the plates is increased by a factor of 21/2and their distance of separation is decreased to half of its initialvalue, calculate the ratio of capacitance in the two cases.

They form a parallel plate capacitor.C=εA/d Where A is the Area of the circular plate.d= 1mm A = πr2So we can write ,C initial C final=επr2/dεπr'2/d'=επr2/dεπr'2/d'=επr2/dεπ(r+2r)2/d/2=r22(r+2r)2 =1/2(1+2)2
The are used in ceiling fans to provide the initial startup energy.

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