H (Noun)
Meaning 1
(thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure; "enthalpy is the amount of energy in a system capable of doing mechanical work".
Classification
Nouns denoting attributes of people and objects.
Examples
- The enthalpy of the gas changed as it expanded and cooled in the container.
- The system's enthalpy increased as it absorbed heat from its surroundings.
- At standard temperature and pressure, the enthalpy of formation of hydrogen peroxide is -187 kilojoules per mole.
- To calculate the enthalpy of the mixture, we need to know its specific heat capacity and the temperatures of its components.
- The change in the enthalpy of the substance during phase transition is an important factor in determining the conditions of the transformation.
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Hypernyms
Meaning 2
A unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second.
Classification
Nouns denoting quantities and units of measure.
Examples
- The unit of inductance known as a henry is defined as the inductance of a closed circuit that produces an electromotive force of one volt in response to a current change of one ampere per second.
- The inductor's measured inductance was 5 h, meaning that within this coil a current change of 1A/s would induce a voltage of 5V.
- The base unit for inductance in the International System of Units is the henry, abbreviated as h.
- A 1 henry inductor produces 1 V when the current through it changes at the rate of 1 A/s.
- A solenoid with an air core and a coil area of 10 cm2 produces 1 h of inductance due to its construction.
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Meaning 3
A nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe.
Classification
Nouns denoting substances.
Examples
- The periodic table lists hydrogen as a highly reactive element, combining easily with oxygen to form water and with carbon to form hydrocarbons.
- Liquid hydrogen has a boiling point of -252.88° C, making it extremely cold and difficult to store.
- The most common isotope of hydrogen is protium, containing one proton in its atomic nucleus.
- The element hydrogen is highly flammable and burns vigorously in air at a wide range of concentrations.
- Free hydrogen atoms are rare in nature, but they are abundant in certain types of stars, particularly main sequence stars like the sun.
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Meaning 4
The constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second.
Classification
Nouns denoting quantities and units of measure.
Examples
- The value of h was a fundamental constant that had to be discovered experimentally.
- In the equation E=hv, h represents the Planck constant.
- The precise measurement of h has been refined over the years to its current accepted value.
- To calculate the energy of a photon, scientists use the formula E=hf, where h is the Planck constant.
- Researchers often use the symbol h to denote the smallest unit of energy in a quantum system.
Synonyms
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Meaning 5
The 8th letter of the Roman alphabet.
Classification
Nouns denoting communicative processes and contents.
Examples
- The typist struggled to type the letter H correctly, often mistaking it for a small L.
- The letter H is the eighth letter of the modern Roman alphabet.
- In some fonts, the letter H is taller than others in order to distinguish it from the letter b.
- Learning to write the letter H in cursive can be a challenging task for many children.
- The origins of the letter H date back to ancient Greek and Phoenician scripts.