Two magnetic dipoles, \(X\) and \(Y,\) are separated by a distance \(d,\) with their axes oriented perpendicular to each other. The dipole moment of \(Y\) is twice that of \(X.\) A charged particle with charge \(q\) moves with velocity \(v\) through their midpoint \(P,\) which makes an angle \(\theta=45^\circ\) with the horizontal axis, as shown in the diagram. Assuming \(d\) is much larger than the dimensions of the dipoles, the magnitude of the force acting on the charged particle at this instant is:

1. \( 0 \) 2. \(\left(\dfrac{\mu_0}{4 \pi}\right) \dfrac{M}{\left(\dfrac{d}{2}\right)^3} \times q v \)
3. \(\sqrt{2}\left(\dfrac{\mu_0}{4 \pi}\right) \dfrac{M}{\left(\dfrac{d}{2}\right)^3} \times q v \) 4. \(\left(\dfrac{\mu_0}{4 \pi}\right) \dfrac{2 M}{\left(\dfrac{d}{2}\right)^3} \times q v\)
Subtopic:  Bar Magnet |
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A bar magnet is demagnetized by inserting it inside a solenoid of length \(0.2~\text{m},~100\) turns, and carrying a current of \(5.2~\text{A}.\) The coercivity of the bar magnet is:
1. \(285~\text{A/m}\) 
2. \(2600~\text{A/m}\)
3. \(520~\text{A/m}\)
4. \(1200~\text{A/m}\)
Subtopic:  Bar Magnet |
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A small bar magnet placed with its axis at \(30^\circ\) with an external 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:
1. \(7.2\times 10^{-2}~\text{J}\)
2. \(11.7\times 10^{-3}~\text{J}\)
3. \(9.2\times 10^{-3}~\text{J}\)
4. \(6.4\times 10^{-2}~\text{J}\)

Subtopic:  Bar Magnet |
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A bar magnet having a magnetic moment of \(2.0\times10^{5}~\text{JT}^{-1}\) is placed along the direction of the uniform magnetic field of magnitude, \(B=14\times10^{-5}~\text{T}\). The work done in rotating the magnet slowly through \(60^\circ \) from the direction of the field is:
1. \(14~\text{J}\)
2. \(8.4~\text{J}\)
3. \(4~\text{J}\)
4. \(1.4~\text{J}\)
Subtopic:  Bar Magnet |
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Two bar magnets oscillate in a horizontal plane in earth’s magnetic field with time periods of 3 s and 4 s respectively. If their moments of inertia are in the ratio of 3 : 2 then the ratio of their magnetic moments will be :
1. 2 : 1
2. 8 : 3
3. 1 : 3
4. 27 : 16
Subtopic:  Bar Magnet |
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A bar magnet with a magnetic moment of \(5~\text{Am}^2\) is initially in a stable equilibrium within a uniform external magnetic field of \(0.4~\text T.\) The work required to slowly rotate the bar magnet into a position of unstable equilibrium is:
1. \(1~\text J\) 
2. \(2~\text J\) 
3. \(3~\text J\) 
4. \(4~\text J\) 
Subtopic:  Bar Magnet |
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A dipole having moment \(M\) is placed in two magnetic fields of strength \(B_1\) and \(B_2\) respectively. If the dipole oscillates \(60\) time in \(20\) s in \(B_1\)  and \(60\) oscillations in \(30\) s in \(B_2\) . Then \(\frac{B_1}{B_2}=\)
1. \(3 \over 2\) 2. \(2 \over 3\)
3. \(4 \over 9\) 4. \(9 \over 4\)
Subtopic:  Bar Magnet |
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