A point charge q is situated a distance a from the center of a conducting sphere of radius R. The sphere is not grounded. Using the method of images, calculate the potential outside the sphere in two different cases: (a) The sphere is neutral and kept at a constant potential V0.
(b) The sphere has total charge Q.
Hint: you will need to add a second image charge besides the one we included in class to solve the problem of the grounded sphere.

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Explanation:

iron would move it is magnetic there is a mag field around the current in the wire

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia