Why is PV work negative ?
Answer me more clearly please sir/mam.
Answer me more clearly please sir/mam.
In this context we are talking about the work done by a gas.
Rather than representing it as w=−PADw=−PAD, think of the formula as representing an area (that the gas is pressing against) moving a distance DD. Since this a change in volume, we can set w=−PΔVw=−PΔV
If you are putting work into the system (say pressing a piston into a cylinder containing a gas at a given pressure), the volume is becoming smaller, so ΔVΔV is negative. The negative of the pressure times a negative ΔVΔV is a positive value, which matches with the sign convention for putting work in. Vice versa, an expansion of a compressed volume at a given pressure will push the piston back out of the cylinder and allow the gas to do work, so ww is negative which follows the sign convention for work output.
In this context we are talking about the work done by a gas.
Rather than representing it as w=−PADw=−PAD, think of the formula as representing an area (that the gas is pressing against) moving a distance DD. Since this a change in volume, we can set w=−PΔVw=−PΔV
If you are putting work into the system (say pressing a piston into a cylinder containing a gas at a given pressure), the volume is becoming smaller, so ΔVΔV is negative. The negative of the pressure times a negative ΔVΔV is a positive value, which matches with the sign convention for putting work in. Vice versa, an expansion of a compressed volume at a given pressure will push the piston back out of the cylinder and allow the gas to do work, so ww is negative which follows the sign convention for work output.
