The area of two parallel plates is doubled and the distance between these plates is also doubled. The capacitor voltage is kept constant. Under these conditions, force between the plates of this capacitor __________(a) decreases(b) increases(c) reduce to half(d) gets doubledI had been asked this question during an interview for a job.My question is based upon Singly Excited Electric Field Systems in chapter Basic Concepts in Rotating Machines of Electrical Machines

The area of two parallel plates is doubled and the distance between th

1.	The area of two parallel plates is doubled and the distance between these plates is also doubled. The capacitor voltage is kept constant. Under these conditions, force between the plates of this capacitor __________(a) decreases(b) increases(c) reduce to half(d) gets doubledI had been asked this question during an interview for a job.My question is based upon Singly Excited Electric Field Systems in chapter Basic Concepts in Rotating Machines of Electrical Machines
Answer» Correct choice is (C) reduce to half The explanation: A2=2A1, x2=2x1, v2=v1, fe2=1/2v^2dC(x)/dx2, C2=ε0A2/x2 ⇒ dC2/dx2 = -ε0A2/x2^2 dC2/dx2 = -2ε0A1/4x1^2 = -ε0A1/2x1^2 ⇒ f&e2 = -1/2v1^2ε0A1/2x1^2 = -1/2(FE1) ⇒ FORCE REDUCES to half.

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