The thickness of a wire significantly impacts the flow of electric current. A thicker wire has a larger cross-sectional area, which reduces its resistance to the flow of electrons. The fundamental relationship between the cross-sectional area (A) of a wire and its resistance (R) is inversely proportional, as indicated by the formula R = ρL/A, where ρ is the resistivity and L is the length of the wire. In simpler terms, when the cross-sectional area increases, resistance decreases, allowing more current to flow through the wire for a given voltage, according to Ohm's Law (V = IR). This is why thicker wires are used in situations where higher current carrying capacity is needed, such as in power transmission lines. The reduced resistance in thicker wires also means less heat is generated due to the current flow, enhancing the efficiency and safety of electrical systems.

Metals conduct electricity better than non-metals primarily due to their atomic structure. In metals, atoms are arranged in a lattice structure, where there are free electrons, often referred to as a 'sea of electrons', that are not bound to any particular atom. These free electrons can move freely throughout the metal, allowing them to easily carry an electric charge. This is in contrast to non-metals, where electrons are more tightly bound to their respective atoms and are not free to move around. Additionally, metals have a lower resistivity compared to non-metals, which also contributes to their superior conductivity. This characteristic of metals is the fundamental reason why they are widely used in electrical wiring and components. The ability of metals to conduct electricity is not only limited to solid state but is also observed in the molten state, further illustrating the role of free electrons in conductivity.

Electron drift velocity is a crucial concept in understanding electric currents. It refers to the average speed at which free electrons in a conductor move under the influence of an electric field. Despite common misconceptions, this velocity is actually quite slow, typically a few millimetres per second. The significance of the electron drift velocity lies not in its magnitude, but in its uniformity and directionality. When a potential difference is applied across a conductor, the free electrons gain a net drift velocity in the opposite direction to the electric field. This uniform motion of electrons constitutes an electric current. It's important to note that the actual movement of electrons is random and erratic due to their thermal energy, but the presence of an electric field imparts a net drift in one direction. The concept of drift velocity helps in understanding how electric currents can be established quickly in a circuit, despite the slow movement of individual electrons.

An electric current typically requires a conducting material to flow, as it is the movement of charges (usually electrons) within a material. However, there are situations where an electric current can exist without a traditional conducting material. One such instance is in a vacuum, where a beam of charged particles, like electrons or ions, can constitute an electric current. This is the principle behind devices such as cathode ray tubes. Another example is in plasma, the fourth state of matter, where ionised gas contains free-moving charged particles that can carry current. While these scenarios are less common than current flowing through metallic conductors, they illustrate that the fundamental requirement for an electric current is the movement of charge, which can occur in various mediums, not limited to solid conductors.

Temperature plays a significant role in affecting the resistance of a conductor, which in turn influences the electric current. As the temperature of a conductor increases, its resistance typically increases. This is due to the increased vibrational energy of the lattice ions in the conductor at higher temperatures, which causes more frequent collisions of free electrons with the ions. These collisions impede the flow of electrons, thereby increasing the resistance. As per Ohm's Law (V = IR), with a constant voltage, an increase in resistance leads to a decrease in current. This relationship is particularly important in practical applications, such as designing circuits that must operate within a range of temperatures. Materials react differently to temperature changes; some materials, like semiconductors, may have decreased resistance with increased temperature. This temperature dependence of resistance is a critical factor in the selection of materials for specific electrical applications.