question_answer 65)

  With the help of a labelled circuit diagram illustrate the pattern of field lines of the magnetic field around a current-carrying straight long conducting wire. How is the right hand thumb rule useful to direction of magnetic field associated with a current-carrying conductor?

Answer:

                  Take a thick straight conductor XV and pass it through the centre of a thick cardboard. Connect the ends of the conductor to the terminals of a battery through a Rheostat Rh, a key K and an ammeter (A) so that the current flows from Y to X. when we sprinkle some iron fillings on the cardboard, these average themselves in concentric circles around O when cardboard is gently tapped. Thus, the pattern of concentric circles indicating the field lines of a magnetic field is observed. These concentric circles represent the magnetic field around a current carrying straight wire become larger and larger as we move away from it. We use right hand thumb rule to find the direction of magnetic field. It follows as imagine the  straight conductor in your right hand such that the thumb points in the direction of current. Then, the direction of asking of fingers of the right hand gives the direction of magnetic lines.