Tiêu đề 05.Magnetism-and-Matter-f.pdf ✅

Physics Smart Booklet 1 5.MAGNETISM AND MATTER Physics Smart Booklet Theory + NCERT MCQs + Topic Wise Practice MCQs + NEET PYQs
Physics Smart Booklet 2

Physics Smart Booklet 4 Field at an arbitrary point due to a bar magnet • For a point P on the axis of a short bar magnet the field is 0 d 3 m B 4 r  =   • For a point  on the equatorial line of a short bar magnet the field is 0 e 3 2m B 4 r  =   • We see that, the field at a certain distance along x axis of a short bar magnet is twice that at the same distance along the equatorial line. Magnetic field along the axis of a solenoid and of a bar magnet Consider a solenoid of length 2l, radius of cross section and ‘a’ having N turns. If n is the number of turns per unit length then, N = n × 2l. Consider a point P at a distance r from the center O of the solenoid. The total magnetic field at point P due to the entire solenoid is 2 0 P 3 NIa B 2r  = (for r >> l and r >> a), Field along (a) the axis of a solenoid and (b) a bar magnet If the radius ‘a’ of the solenoid is very small compared to r, we get, or 0 P 3 2NIA B 4 r  =   where A = a 2 is area of cross section of the solenoid 0 P 3 2m B 4 r  =  ...(1) where m = NIA is magnetic moment of the solenoid. This equation is similar to the equation for the magnetic field due to a short bar magnet on the axial line 0 P 3 2m B 4 r  =  ...(2) m represents the magnetic moment of the magnet, which is the product of its pole strength and magnetic length. The resemblance of Eqs., (1) and (2) reveal the equivalence of a solenoid and a bar magnet. Magnetic Charge or Pole Strength Magnetic moment m = n(2l)IA = nIA (2l) i.e., m = nIA (2l) ...(3) The electric field on the axial line of a short dipole is also given by a similar equation. 3 0 1 2p E 4 r =  ...(4) Field points on the axis and equatorial line for a short bar magnet