What is generated within a conductor when current flows through it?

When current flows through a conductor, one of the key phenomena that occurs is the generation of heat due to the resistance offered by the material of the conductor to the flow of electric current. This heat generation is a result of the collisions between the flowing electrons and the lattice structure of the material, which converts some of the electrical energy into thermal energy. This phenomenon is known as Joule heating, named after the physicist James Prescott Joule, who first studied the relationship between electric current, resistance, and heat.

While it is true that other effects such as magnetic fields are also generated in a conductor when current flows through it, it is the heat generation that is the most direct consequence when considering typical resistive conductors. Sound waves and light can also be produced under certain specific conditions (e.g., in the case of a loudspeaker or a light bulb, respectively), but these are not the generic or primary outcomes of current flow in standard conductive materials. Thus, heat production is the most straightforward and common result, making it the correct answer in this context.