Which best describes electromagnetic waves? A. transverse waves made up of electric and magnetic fields

B. longitudinal waves made up of vibrations that move through matter

C. mechanical waves that travel as ripples in water

D. sound waves that can only travel in a medium

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.