At some location on earth the horizontal component of earth's magnetic field is 18 × 10–6 T. At this location, magnetic needle of length 0.12 m and pole strength 1.8 Am is suspended from its mid-point using a thread, it makes 45º angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is
(1) 1.8 × 10–5 N
(2) 6.5 × 10–5 N
(3) 3.6 × 10–5 N
(4) 1.3 × 10–5 N
