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# Heat and Temperature Study Guide for McGraw-Hill's Firefighter Exams (page 2)

By McGraw-Hill Professional
Updated on Jun 25, 2011

#### Celsius Degree

The Celsius (C) degree is a metric unit of temperature measurement. It is named for the Swedish professor Anders Celsius, who invented the Centigrade temperature scale in the 1720s using the freezing point of water as 0 degrees and the boiling point of water as 100 degrees. This unit is approved by the SI.

To convert (approximately) normal body temperature on the Centigrade scale to the Fahrenheit scale, first multiply the Celsius temperature by 1.8, or 9/5, and then add 32.

#### Rankine Degree

The Rankine (R) degree is a traditional unit of absolute temperature. The temperature units for Rankine and Fahrenheit are equal (1 degree Rankine represents the same temperature difference as 1 degree Fahrenheit), but the zero points differ. The zero point on the Rankine scale is set at absolute zero, which is –457.6 degrees, the hypothetical point at which all molecular movement ceases. The unit is named for British physicist and engineer William Rankine (1820–1872).

To convert degree units from the Rankine scale to the Fahrenheit scale and the Fahrenheit scale to the Rankine scale use the following formulas:

F = R – 457 and R = F + 457

#### Kelvin Degree

The Kelvin degree (K) is equal to the Celsius degree, but the Kelvin scale has its zero point set at absolute zero, which is –273.1. This unit is approved by the SI. The Kelvin degree is named for British inventor and scientist William Thompson, who was knighted by Queen Victoria in 1866 and named Baron Kelvin of Largs in 1892.

To convert degree units from the Kelvin scale to the Centigrade scale and the Centigrade scale to the Kelvin scale, use the following formulas:

C = K – 273 and K = C + 273

### Heat Transfer

Heat can be transferred to other materials through conduction, convection, radiation, and direct flame contact.

#### Conduction

Conduction is the transfer of heat energy through a medium (usually a solid). Heat causes molecules within the material to move at a faster rate and transmit their energy to neighboring molecules. The heat of conduction can also be transferred from one material to another via direct contact in the same fashion as internal molecular movement. The amount of heat transferred and rate of travel is dependent on the thermal conductivity of the material. Dense materials (metals) are good conductors of heat energy. Fibrous materials (wood, paper, cloth) and air are poor conductors. In a fire situation, heat can be conducted via steel columns and girders to abutting wood floor joists causing them to smolder and eventually ignite.