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18/09/2020 6:22 pm
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A circular coil has moment of inertia 0.8 kg m2 around any diameter and is carrying current to produce a magnetic moment of 20 am2. The coil is kept initially in a vertical position and it can rotate freely around a horizontal diameter. When a uniform magnetic field of 4T is applied along the vertical, it starts rotating around its horizontal diameter. The angular speed the coil acquires after rotating by 60° will be :
(1) 20 rad s–1
(2) 10 rad s–1
(3) 20 π rad s–1
(4) 10π rad s–1
1 Answer
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18/09/2020 6:27 pm
(2) 10 rad s–1
Explanation:
From energy conservation
1/2Iω2
= Uin - Ur
= – MB cos60º – (–MB)
MB/2 = 1/2Iω2
20 x 4/2 = 1/2(0.8)ω2
100 = ω2
ω = 10 rad