Temperature
Physics · तापमान
📋Quick Overview
Temperature is the measure of hotness or coldness of a body. It tells us the degree of heat energy in an object. Heat flows from a hotter body to a colder body until both reach the same temperature (thermal equilibrium). Temperature is NOT the same as heat — temperature is the measure, heat is the energy.
📖Temperature Scales
| Scale | Symbol | Freezing Point of Water | Boiling Point of Water | Inventor |
|---|---|---|---|---|
| Celsius | °C | 0°C | 100°C | Anders Celsius |
| Fahrenheit | °F | 32°F | 212°F | Daniel Fahrenheit |
| Kelvin | K | 273.15 K | 373.15 K | Lord Kelvin |
⭐
Kelvin is the SI unit of temperature. Kelvin scale has NO negative values. 0 K = Absolute Zero = -273.15°C = the lowest possible temperature where all molecular motion stops.
📖Temperature Conversion Formulas
| Conversion | Formula | Example |
|---|---|---|
| °C to °F | °F = (9/5 × °C) + 32 | 37°C = (9/5 × 37) + 32 = 98.6°F (body temp) |
| °F to °C | °C = 5/9 × (°F - 32) | 212°F = 5/9 × (212-32) = 100°C |
| °C to K | K = °C + 273.15 | 100°C = 373.15 K |
| K to °C | °C = K - 273.15 | 0 K = -273.15°C |
⭐
-40° is the SAME on both Celsius and Fahrenheit scales! (-40°C = -40°F). This is a favorite exam trick question.
📖Types of Thermometers
| Thermometer Type | Used For | Range / Details |
|---|---|---|
| Clinical (Mercury) | Human body temperature | 35°C to 42°C; has a kink to prevent mercury from falling back |
| Laboratory Mercury | Lab experiments | -10°C to 110°C |
| Digital Thermometer | Body/room temperature | Electronic sensor, quick reading |
| Pyrometer | Very high temperatures (furnaces, sun) | Can measure without contact |
| Maximum-Minimum Thermometer | Daily max/min temperature (weather) | Records highest and lowest temperature of day |
📝Important Facts about Temperature
- •Normal human body temperature = 37°C = 98.6°F = 310.15 K
- •Absolute Zero = 0 K = -273.15°C = -459.67°F (lowest possible temperature)
- •At absolute zero, all molecular motion stops
- •Mercury freezes at -39°C, so alcohol thermometers are used in very cold regions
- •Thermal equilibrium: Two bodies at same temperature — no heat flows between them (Zeroth Law of Thermodynamics)
- •Heat always flows from higher temperature to lower temperature