An infinitely long wire carrying a 25-A current in a the positive x-direction is places along the xaxis in the vicinity of a 20-turn circular loop located in the x-y plane. If the magnetic field at the center of the loop is zero, what is the direction and magnitude of the current flowing in the loop

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.