Fig. 28-2 shows four different sets of wires that cross each other without actually touching. the magnitude of the current is the same in all four cases, and the directions of current flow are as indicated. for which configuration will the magnetic field at the center of the square formed by the wires be equal to zero?

What is the most useful equation for electric power?

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.

14. a body is projected with velocity vi from a.at the same time another body is projectedvertically upwards from point b withvelocity v2 lies vertically below the highestpoint. both the bodies collide thenv2÷v1is