Explain the origin of resistance in a conductor. Can a conductor have no resistance?
The correct answer and explanation is:
Correct Answer:
The origin of resistance in a conductor lies in the collisions between free electrons and the atoms or imperfections in the material as electric current flows. A conductor cannot have zero resistance under normal conditions, but under certain special conditions, like superconductivity, it can.
Explanation (300 words):
Electric current in a conductor, such as copper or aluminum, is the movement of free electrons through the material. These free electrons are not bound to individual atoms and can move under the influence of an electric field. However, their motion isn’t smooth or uninterrupted.
As the electrons move, they constantly collide with the fixed positive ions of the conductor’s atomic lattice. Each collision causes the electrons to lose some energy in the form of heat. This energy loss due to electron-lattice collisions is what we call electrical resistance.
The degree of resistance depends on several factors:
- Material type: Conductors like silver or copper have lower resistance because their atomic structures allow easier electron flow.
- Temperature: As temperature increases, the atomic lattice vibrates more, increasing the number of collisions, and thus, the resistance.
- Length and thickness of the conductor: Longer conductors have more resistance, and thicker ones have less because there is more area for electrons to flow.
Under normal conditions, all conductors have some resistance. However, certain materials exhibit a phenomenon called superconductivity at extremely low temperatures (close to absolute zero). In this state, resistance drops to zero, and electrons flow without any energy loss. This only occurs in specific materials like some ceramics or elemental metals cooled with liquid helium or nitrogen.
In practical applications, even the best conductors (like silver or copper) still have a small, non-zero resistance. So, in summary, while superconductors can achieve zero resistance under specific conditions, ordinary conductors always exhibit some resistance due to electron collisions.