A magnetic needle of length 10cm, suspended at its middle point through a thread, stays at a an angle of `45^@` with the horizontal. The horizontal component of the earth's magnetic field is `18 muT`. (a) Find the vertical component of this field. (b) If the pole strength of the needle is `1.6 A-m`, what vertical force should be applied to an end so as to keep it in horizontal position?

Answer

`18 mu T , 5.8 xx 10^(-5) N `