A spherical cavity is excised from the inside of the sphere. The cavity has radius a4 and is centered at position h⃗ , where |h⃗ |<34a , so that the entire cavity is contained within the larger sphere. Find the electric field inside the cavity.

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.