The presence of which magnetic feature best explains why a magnet can act at a distance on other magnets or on objects containing certain metals? a) fields b) dipoles c) domains d) forces

Answer

A.Fields

Explanation

The presence of a magnetic field best explains why a permanent magnet can act upon another magnetic object whilst being at some distance. Magnetic field lines emanate from the north pole, curve around the magnet and reconnect to the south pole. The strength of the magnetic field lines decrease as you get further away from the magnet.  

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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