If a current of 2. 4 a is flowing in a cylindrical wire of diameter 2. 0 mm, what is the average current density in this wire?.

Which of the following represents a virtual image?

The electric field between square plates of a parallel-plate capacitor has magnitude e. the potential across the plates is maintained with constant voltage by a battery as they are pulled apart to twice their original separation, which is small compared to the dimensions of the plates. the magnitude of the electric field between the plates is now equal to a)e b)e/4 c)e/2 d)4e e)2e

It is really hard for me right know