AP EAMCET2009PhysicsMagnetic Effects of Current
Two bar magnets A and B are placed one over the other and are allowed to vibrate in a vibration magnetometer. They make 20 oscillations per minute when the similar poles of A and B are on the same side, while they make 15 oscillations per minute when their opposite poles lie on the same side. If M_A and M_B are the magnetic moments of A and B and if M_A>M_B , the ratio of M_A and M_B is
Options
- A4: 3
- B25:7
- C7:5
- D25:16
Correct answer
C. 7:5
Step-by-step solution
Ratio of magnetic moments of two magnets of equal size when in sum and difference position is M_A M_B = T_d^2+T_s^2 T_d^2-T_s^2 = v_s^2+v_d^2 v_s^2-v_d^2 aligned & = ( 1 20 )^2+ ( 1 15 )^2 ( 1 15 )^2- ( 1 20 )^2 & = 400+225 400-225 & = 625 175 = 25 7 aligned M_A: M_B=25: 7