A small bar magnet is placed with its axis at 30 o with an external magnetic field of 0 . 06 T experiences a torque of 0 . 018 Nm . The minimum work required to rotate it from its stable to unstable equilibrium position is:

Question

A small bar magnet is placed with its axis at 30 o with an external magnetic field of 0 . 06 T experiences a torque of 0 . 018 Nm . The minimum work required to rotate it from its stable to unstable equilibrium position is:, 6 . 4 × 10 − 2 J, 9 . 2 × 10 − 3 J, 7 . 2 × 10 − 2 J, 11 . 7 × 10 − 3 J

MARKS App · Accepted Answer

τ = MBsinθ = 0 . 018 M = 0 .018 B sin θ = 0 .018 0 .06 × 0 .5 = 0 .64 A m 2 W = ΔU = U f − U i = − MB cos 180 ∘ − − MB cos 0 ∘ = 2 MB = 2 × 0 .6 × 0 .06 = 0 . 072 J

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