JEE Main 2019 Physics question
Not in JEE Advanced syllabus
At some location on earth the horizontal component of earth's magnetic field is 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° angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is:
Answer: (D)
Solution
T; ⇒ F = 2mB ≈ N.