Science · X-Factor Notes
Conductivity revision notes for UPPCS Prelims.
14 revision facts
| Concept | What to remember | Asked in UPPCS |
|---|---|---|
| Conductor Definition | A substance or material that allows electricity to flow through it. Conductors possess a large number of free electrons. They are characterized by low resistance and high thermal conductivity. | |
| Best Electrical Conductor | The most electrically conductive element is Silver, followed by copper, aluminium, and iron. | UPPCS (Mains) 2015, UPPCS (Mains) 2012 |
| Protection from Lightning | A closed car protects its occupants from lightning because the closed car behaves like a Faraday cage (a closed hollow conductor) where the electric field or charge inside is always zero. | U.P. R.O./A.R.O. (Pre) 2023 |
| Lightning Conductor Material | Copper rods are preferred over iron for lightning conductors because copper is a better conductor of electricity than iron and is not easily oxidized under atmospheric conditions. | U.P. R.O./A.R.O. (Mains) 2013 |
| Thomson Effect | Due to temperature variation along a conductor, potential variation occurs along it; this phenomenon is known as the Thomson effect. |
| Concept | What to remember | Asked in UPPCS |
|---|---|---|
| Conduction Mechanism | Electric conduction in a semiconductor takes place due to both electrons and holes. | |
| Effect of Heat on Resistance | On heating, the resistance of a semiconductor decreases. | |
| Resistance at Absolute Zero | At absolute zero temperature (0 K), the electric resistance in a semiconductor is infinite. At this temperature, semiconductors behave like an insulator. | |
| Transistor Material | Germanium and Silicon are the main elements used as semiconductors in transistors. | U.P. R.O./A.R.O. (Pre) 2016, UPPCS (Mains) 2005 |
| Most Common Transistor Material | Silicon is the most commonly used material for making transistors. Silicon is generally favored because it can be used at much higher temperatures than Germanium. | UPPCS (Pre) 2015, U.P. P.C.S. (Pre) 2018 |
| Concept | What to remember | Asked in UPPCS |
|---|---|---|
| Superconductor Definition | Superconductors are characterized by zero permeability and zero electrical resistance. | |
| Discovery and Transition Temperature | Superconductivity was discovered in 1911 by Dutch physicist Heike Onnes, initially only near absolute zero (–273.15°C). Examples of transition temperatures include Mercury (4.2 K) and Lead (7.2 K). | |
| Economic Impact | If superconductivity could be achieved at room temperature, it would lead to tremendous economic savings by preventing power loss during electric transmission. | UPPCS (Pre) 2000 |
| High Temperature Superconductors | The newly discovered high temperature superconductors are generally ceramic oxides. | UPPCS (Pre) 2000 |
