| Calorie: | A unit of heat, 1Calorie = 4.186 joules. |
| Candela: | The S.I. unit of luminous intensity defined as the luminous intensity in a given direction of a source that emits monochromatic photons of frequency 540 x 1012 Hz & has a radiant intensity in that direction of 1/683 W/sr |
| Capacitance: | The ratio of charge stored per increase in potential difference. |
| Capacitor: | Electrical device used to store charge and energy in the electrical field. |
| Capillarity: | The rise or fall of a liquid in a tube of very fine bore. |
| Carnot's theorem: | No engine operating between two temperatures can be more efficient than a reversible engine working between the same two temperatures. |
| Centrifugal force: | An outward pseudo force acting on a body in circular motion. |
| Centripetal force: | The radial force required to keep an object moving in a circular path; it is equal to mv2/r. |
| Charles' law: | For a given mass of a gas at constant pressure, the volume is directly proportional to the temperature. |
| Chromatic aberration: | An optical lens defect causing color fringes, because the lens brings different colors of light to focus at different points. |
| Clausius' statement of second law of Thermodynamics: | It is not possible that at the end of a cycle of changes heat has been transferred from a colder body to a hotter body without producing some other effect. |
| Closed system: | The system which cannot exchange heat or matter with the surroundings. |
| Coefficient of linear expansion: | The increase in length per unit original length per degree rise in temperature. |
| Coefficient of superficial expansion: | The increase in area per unit original area per degree rise in temperature. |
| Coefficient of volumetric expansion: | The increase in volume per unit original volume per degree rise in temperature. |
| Coherent source: | A source in which there is a constant phase difference between waves emitted from different parts of the source. |
| Condensation point: | The temperature at which a gas or vapor changes back to liquid. |
| Conduction: | The transfer of heat from a region of higher temperature to a region of lower temperature by increased kinetic energy moving from molecule to molecule. |
| Convection: | The transfer of heat by the actual transfer of matter. |
| Coulomb's law: | The force between any two charges is directly proportional to the product of charges and inversely proportional to the square of the distance between the charges. |
| Critical angle: | The angle of incidence in a denser medium for which angle of refraction is . |
| Cyclotron: | A device used to accelerate the charged particles. |
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