The source of heat for a (an) system is electricity

Electric Heating systems use electricity as a source of heat.

Explanation:

Each heater consists of an electric resistor, which the heating element in it. The process involved is Joule Heating. It is the phenomenon in which, passage of electric current produces heat. Heat is generated when the electrons from the current and the positive ions of the conductor start interaction.

The presence of voltage difference makes an electric fields, which in turn accelerates the charges present in the conductors. When they collide with ions of conductor, heat gets generated, and emitted out, which we use for heating purposes.

i think it because equal matrices have equal dimensions, only square matrices can be symmetric. for all indices and . every square diagonal matrix is symmetric, since all off-diagonal elements are zero. in linear algebra, a real symmetric matrix represents a self-adjoint operator over a real inner product space.