Which SI base unit measures temperature?

Which SI base unit measures temperature?

• A. Kelvin (K)
• B. Celsius
• C. Fahrenheit
• D. Rankine

Answer: (A)

The basic idea is that temperature as a fundamental quantity in science is measured with the Kelvin as the SI base unit. Kelvin provides an absolute temperature scale where zero is absolute zero (the complete absence of thermal energy), and each unit increase represents a fixed amount of energy as defined by the Boltzmann constant. This makes Kelvin ideal for calculations in thermodynamics and chemistry, because equations involving energy, entropy, and phase transitions rely on an absolute temperature scale. Other scales like Celsius and Fahrenheit are widely used in everyday life, but they’re not SI base units. Celsius is tied to water’s freezing and boiling points and uses an offset from absolute zero (0 °C = 273.15 K), so it isn’t an independent SI unit. Fahrenheit is another common scale with its own reference points, and Rankine is an absolute-scale used mainly in some engineering contexts but is not part of the SI. In fact, Kelvin and Rankine are related by a simple conversion (1 K = 9/5 R), but Kelvin remains the SI base unit. So, Kelvin is the correct choice because it is the SI base unit for thermodynamic temperature.

The basic idea is that temperature as a fundamental quantity in science is measured with the Kelvin as the SI base unit. Kelvin provides an absolute temperature scale where zero is absolute zero (the complete absence of thermal energy), and each unit increase represents a fixed amount of energy as defined by the Boltzmann constant. This makes Kelvin ideal for calculations in thermodynamics and chemistry, because equations involving energy, entropy, and phase transitions rely on an absolute temperature scale.

Other scales like Celsius and Fahrenheit are widely used in everyday life, but they’re not SI base units. Celsius is tied to water’s freezing and boiling points and uses an offset from absolute zero (0 °C = 273.15 K), so it isn’t an independent SI unit. Fahrenheit is another common scale with its own reference points, and Rankine is an absolute-scale used mainly in some engineering contexts but is not part of the SI. In fact, Kelvin and Rankine are related by a simple conversion (1 K = 9/5 R), but Kelvin remains the SI base unit.

So, Kelvin is the correct choice because it is the SI base unit for thermodynamic temperature.