24. Electric Force & Field; Gauss' Law

A cube has sides equal to $4.0\mathrm{cm}$. The net flux through the cube is $12\mathrm{N}·{\mathrm{m}}^2/\mathrm{C}$ outward. Is the net charge in the cube positive, negative or zero?

An electric field with strength $3500\mathrm{N}/\mathrm{C}$ exists just outside a face of a large block of aluminum. If the electric field points towards the block, what is the surface charge density on the face of the block?

A sphere of radius $4.0\mathrm{cm}$ has a charge of $23\mathrm{nC}$ evenly distributed throughout the sphere. What is the electric field strength $1.0\mathrm{cm}$ from the center of the sphere?

An insulating sphere of radius $4.0\mathrm{cm}$ is in the center of a conducting spherical shell with inner radius of $5.0\mathrm{cm}$ and outer radius of $7.0\mathrm{cm}$. The insulating sphere has a charge of $-34\mathrm{nC}$ and the conducting spherical shell has a net charge of $42\mathrm{nC}$. What is the total charge on the inner surface of the conducting spherical shell?

A very long insulating cylinder has radius $4.7\mathrm{cm}$. Every $3.0\mathrm{m}$ length of the cylinder contains a charge of $86\mathrm{nC}$ evenly distributed throughout. What is the strength of the electric field $3.0\mathrm{cm}$ from the axis of the cylinder?