Question

A nervous physicist worries that the. two metal shelves of his wood frame bookcase might obtain a high voltage difference if charged by static electricity, perhaps produced by friction.

Part (a) What is the capacitance of the empty shelves if they have area 0.85 x 10³ cm² and are 0.21 m apart in F?

Part (b) What is the potential difference between them if opposite charges of magnitude 2.00 nC are placed on them in V?

 Part (c) To show that this voltage poses a small hazard, calculate the energy stored in I.

Answer 1

a.) C = € A/ d = 8.854 E-12 × 0.085 / 0.21 = 3.58E-12F

b.) V = Q/C = 2E-9/3.58E-12 = 558.66v

c.) U = 1/2 × CV^2 = 0.5 × 3.58E-12 × (558.66)^2 = 0.558 E-6 Joule

Hence U = 0.6 micro Joule.

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