Question

A thin, horizontal 11cm×11cm11cm×11cm copper plate is charged with 1.7×10¹⁰ electrons. Consider the electrons are uniformly distributed on the surface.

Part A

What is the strength of the electric field 0.1 mmmm above the center of the top surface of the plate?

Express your answer using two significant figures.

Part B

What is the direction of the electric field 0.1 mmmm above the center of the top surface of the plate?

What is the direction of the electric field 0.1 above the center of the top surface of the plate?

away from the plate

toward the plate Part C What is the strength of the electric field at the plate's center of mass? Part D What is the strength of the electric field 0.1 mmmm below the center of the bottom surface of the plate? Express your answer using two significant figures. Part E What is the direction of the electric field 0.1 mmmm below the center of the bottom surface of the plate? Please I am stuck in this question. I am confused with the 1.7*10^10 electrons

Answer 1

given

Area, A = 11*11 cm^2

= 121 cm^2

= 121*10^-4 m^2

= 0.0121 m^2

magnitude of charge, Q = 1.7*10^10 e

= 1.7*10^10*1.6*10^-19

= 2.72*10^-9 C

magnitude of surface charge density, sigma = Q/A

= 2.72*10^-9/0.0121

= 2.248*10^-7 C/m^2

A) strength of the electtric field 0.1 mm above center of the top surface of the plate,

E = sigma/(2*epsilon)

= 2.248*10^-7/(2*8.854*10^-12)

= 1.3*10^4 N/C

B) towards the plate.
Because, the plate has negative charge.

C) Zero.

Because, inside a conductor in electrostatic equilibrium electric field is zero.

D) strength of the electtric field 0.1 mm below the center of the bottom surface of the plate,

E = sigma/(2*epsilon)

= 2.248*10^-7/(2*8.854*10^-12)

= 1.3*10^4 N/C

E) towards the plate.
Because, the plate has negative charge.

Note : A positive charge always produce electric field radially outward and a negative charge always produce electric field radially inward.