"the current in a long wire creates a magnetic field in the region around the wire". How is the strength of the field at distance r from the wire center related to the magnitude of the field? field directly proportional to r field inversely proportional to r field directly proportional to r2 field inversely proportional to r2

In a heat engine if 1000 j of heat enters the system the piston does 500 j of work, what is the final internal energy of the system if the initial energy was 2000 j? 1. write the equation 2.list out your known variables 3.plug the numbers into the equations 4.solve 5.write your solution statement that includes initial energy and final