Many stereo speaker cables are made of copper wire surrounded by rubber. The electricity travels down the copper portion of the cable while the rubber protects you from being "zapped" by the electricity. Which physical property explains the difference in ability of copper and rubber to transmit electricity?

Conductivity.

Explanation:

Conductivity is the physical property that explains the difference in ability of copper and rubber to transmit electricity. Basically transmission of electricity or electric current is possible due to the movement of electrons. There are free electrons in the copper while in rubber there are no free electrons. When electrons move in the direction, an electric current flows in the opposite direction. This phenomenon is also known as conductivity i.e. ability to conduct current.

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