JEE Main 201910 Jan, Evening shiftPhysicsHardMagnetic Effects of Current and Magnetism165× since 2002
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 45^o angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is -