Saved Bookmarks
| 1. |
(a) State Ampere's cicuital law. Use this law to obtain the expression for the magnetic field inside an air cored toriod of average radius 'R',having 'n' truns per unit length and carrying a steady current I. (b) An observer to the left of a solenoid of N turns each of cross section area 'A' observes that a steady current I in it flows in the clockwise direction. Depict the magnetic field lines due to the solenoid specifying its polarity and show that it acts as a bar magnet of magnetic moment m = NIA. |
Answer» Solution :(b) The magnetic FIELD lines due to the solenoid are depicted in the fig. The solenoid coilbehaves as a magnetic dipole in which the left END of solenoid , from which side the observer observes the steady current I to FLOW in the clockwise direction, exhibits south (S) polarity and right end the north (N) polarity.  We know that a current carrying closed loop PRODUCES a magnetic field similar to that of a magnetic dipole and the magnetic moment `vecm` of the current loop is given by `vecm = I VECA `, where `vecA` is the area vector of the loop. In a solenoid magnetic field and hence magnetic moment of all the N turns, carrying same current in same direction, is added up. As a result, the current carrying solenoid acts as a bar magnet whose magnetic moment m = N (magnetic moment due to a single current loop) `implies vecm = N I vecA`. |
|