3. Which of the following does not affect the resistance of a wire? (a) temperature (b)density (c)length (d) chemical composition

The correct answer is (b) density.<br /><br />Here's why:<br /><br />* **Temperature:** Resistance generally increases with temperature in conductors. Higher temperatures cause the atoms in the material to vibrate more, which increases the likelihood of collisions with moving electrons, thus hindering their flow and increasing resistance.<br /><br />* **Length:** A longer wire has more resistance than a shorter wire of the same material and cross-sectional area. Electrons have to travel a greater distance, encountering more resistance along the way.<br /><br />* **Chemical Composition:** Different materials have different inherent resistivities. The resistivity of a material is a measure of how strongly it opposes the flow of electric current. For example, copper has a lower resistivity than iron, meaning copper is a better conductor.<br /><br />* **Density:** The density of a material, which is its mass per unit volume, does not directly affect its resistance. Resistance is primarily determined by the factors listed above. While density might indirectly relate to other material properties that *do* affect resistance, it's not a primary factor itself.<br />