Work of gas is carried out at change of its volume. At change of volume of gas, nodes of heat engines, whether it be the internal combustion engine or a bullet in a gun trunk start moving. At various processes, work of gas is calculated differently.
It is required to you
- - manometer;
- - thermometer.
1. If work of gas is carried out at isobaric process (with a constant pressure), then to find a job of gas by means of the manometer, measure gas pressure. After that measure its volume before performance of work and later. Find change of volume of gas, having taken away initial from final value. After that find the work of pressure of gas upon change of its volume. It will also be work of gas with a constant pressure of A=p•ΔV.
2. For ideal gas it is possible to calculate work with a constant pressure, having applied Klapeyrona-Mendeleyev's equation. Find a gas job, having increased its weight by number 8.31 (universal gas constant) and temperature change when performing work. Divide result into the molar mass of A=m gas • R•ΔT/M. When calculating consider that if work is performed by gas (it extends), then it is positive. If work is performed over gas (it is compressed by third-party forces), then work is negative.
3. If work carries out at isothermal expansion (when temperature is constant), learn change of volume of gas and value of its temperature. To find a gas job, increase its weight by number 8.31 (universal gas constant) and temperature when performing work. Divide result into the molar mass of gas. Increase the turned-out number by a logarithm natural of the relation of final and initial volumes of A=m gas • R · T • ln(V2/V1)/M.
4. Generally, to find a job of gas take integral from function of pressure on volume. Integral borders – from ∫pdV, initial up to the final volume. If there is a schedule of gas process in coordinates (V, p), as a rule, it represents a straight line, find the area of a trapeze limited lines by Vv perpendicular to an axis points of V1 and V2, from below axis V on each side, and from above a function graph. In more difficult cases the area of a curvilinear trapezoid is looked for.