A nervous physicist worries that the two metal shelves of hi

A nervous physicist worries that the two metal shelves of his wood frame bookcase might obtain a high voltage if charged by static electricity, perhaps produced by friction. What is the capacitance of the empty shelves if they have area 0.375 m2 and are 0.155 m apart?

F?

What is the voltage between the two shelves if opposite charges of magnitude 1.25 × 10-9 C are placed on them?

V?

Calculate the energy stored by having this charge on the two shelves.

J?

Solution

area , A = 0.375 m^2

d = 0.155 m

capacitance of the metal strips = epsilon * A /d

capacitance of the metal strips = 8.854 *10^-12 * 0.375/.155

capacitance of the metal strips = 2.142 *10^-11 F

voltafge , V

as Q = C * V

1.25 *10^-8 = 2.142 *10^-11 * V

V = 583.3 V

the voltage between the sherves is 583.3 V

energy stored = 0.5 * C * V^2

energy stored = 0.5 * 2.142 *10^-11 * 583.5^2

energy stored = 3.647 *10^-6 J

the energy stored by these shelves is 3.647 *10^-6 J