Question

Distinguish between isobar and isotherm.

Answer 1

Hint: Isobars and isotherms are lines or contours on a map that join points having the same pressure and temperature respectively. Isobars and isotherms have varied purposes especially in the fields of thermodynamics and geography.

Complete answer:

Isobar	Isotherm
1) It is the contour or line joining the points on a map or a thermodynamic plot of an ideal gas for which the pressure remains constant.	1) It is the contour or line joining the points on a map or a thermodynamic plot of an ideal gas for which the temperature remains constant.
2) In geographical terms, an isobar will be the curve joining the locations on a map where the pressure is the same.	2) In geographical terms, an isotherm will be the curve joining the locations on a map where the temperature is the same.
3) In thermodynamics, an isobar is obtained when the gas undergoes an isobaric process (its pressure remains constant throughout).	3) In thermodynamics, an isotherm is obtained when the gas undergoes an isothermal process (its temperature remains constant throughout)
4) The internal energy of an ideal gas can change when going on an isobar.	4) The internal energy of an ideal gas remains constant when going on an isotherm.

Note:
Students must note that in the field of thermodynamics there is another curve called the isochore. This is the line or contour joining all the points on a thermodynamic plot between a gas’s pressure and temperature where the volume of the gas remains constant, that is, while travelling on this curve, the gas neither expands or contracts. In a sense, it can also be said that on the isochore, the gas does not do any mechanical work.