Due to a small magnet, the intensity at a distance \(x\) in the end-on position is \(9~\text{gauss}\). What will be the intensity at a distance \(\dfrac{x}{2}\) on equatorial position?
1. \(9~\text{gauss}\) 2. \(4~\text{gauss}\)
3. \(36~\text{gauss}\) 4. \(4.5~\text{gauss}\)
Subtopic:  Bar Magnet |
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A \(100\)-turn coil of wire of size \(2~\text{cm}\times 1.5~\text{cm}\) is suspended between the poles of a magnet producing a field of \(1~\text T,\)  inside a galvanometer. Calculate the torque on the coil due to a current of \(0.1~\text{A}\) passing through the coil.
1. \(3 \times 10^{-5}\) N-m 
2. \(30\) N-m
3. \(3 \times 10^{-3}\) N-m 
4. \(3 \times 10^{-2}\) N-m 
Subtopic:  Bar Magnet |
 82%
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A solenoid of cross-sectional area \(2\times 10^{-4}~\text{m}^2\) and \(1000\) turns placed with its axis at \(30^\circ\) with an external field of \(800~\text{G}\)experiences a torque of \(0.016~\text{Nm}.\)The current flowing through the solenoid is:
1. \(2~\text{A}\)
2. \(4~\text{A}\)
3. \(1~\text{A}\)
4. 
\(5~\text{A}\)

Subtopic:  Bar Magnet |
 65%
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The length of a magnetized iron bar is \(L\) and its magnetic moment is \(M.\) When this bar is bent to form a semicircle its magnetic moment is:
1. \(M\) 2. \(\dfrac{M\pi}{2}\)
3. \( \dfrac{M}{2\pi}\) 4. \(\dfrac{2M}{\pi}\)
Subtopic:  Bar Magnet |
 77%
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NEET - 2024
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The magnetic moment of an iron bar is \(M.\) It is now bent in such a way that it forms an arc section of a circle subtending an angle of \(60^\circ\) at the centre. The magnetic moment of this arc section is:
1. \(\dfrac{3 M}{\pi}\) 2. \(\dfrac{4M}{\pi}\)
3. \(\dfrac{ M}{\pi}\) 4. \(\dfrac{2 M}{\pi}\)
Subtopic:  Bar Magnet |
 78%
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NEET - 2024
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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 short bar magnet placed with its axis at \(30^{\circ}\) with an external field of \(800~\text{G}\) experiences a torque of \(0.016~\text{N-m}\). What is the work done in moving it from its most stable to the most unstable position?
1. \(0.036~\text{J}\)
2. \(0.016~\text{J}\)
3. \(0.064~\text{J}\)
4. \(0\)

Subtopic:  Bar Magnet |
 71%
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In a uniform magnetic field of \(0.049~\text T\), a magnetic needle performs \(20\) complete oscillations in \(5\) seconds as shown. The moment of inertia of the needle is \(9.8 × 10^{-6} ~\text{kg m}^2\). If the magnitude of magnetic moment of the needle is \(x \times 10^{-5 }~\text {Am}^2;\) then the value of '\(x\)' is:
         
1. \(128\pi^2\) 2. \(50\pi^2\)
3. \(1280\pi^2\) 4. \(5\pi^2\)
Subtopic:  Bar Magnet |
 53%
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NEET - 2024
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Four small identical bar magnets, each of magnetic dipole moment \(M\), are placed on the vertices of a square of side \(a\) such that the diagonals of the square coincide with the perpendicular bisectors of the respective magnets. The net magnetic field at the centre of the square is:

           
1. zero

2. \(\dfrac{\mu_{0}}{\sqrt{2 \pi}} \dfrac{M}{a^{3}}\)

3. \(\dfrac{2 \sqrt{2} \mu_{0}}{\pi} \cdot \dfrac{M}{a^{3}}\)

4. \(\dfrac{\mu_{0}}{\pi} \cdot \dfrac{M}{a^{3}}\)

Subtopic:  Bar Magnet |
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A small permanent magnet is placed 'antiparallel' to a uniform magnetic field \(B.\) A null point is found at a distance \(r,\) on the axis of the magnet. Then, \(r\) is proportional to (nearly):
1. \(B^{-3}\) 2. \(B^{-2}\)
3. \(B^{-1/2}\) 4. \(B^{-1/3}\) 
Subtopic:  Bar Magnet |
 71%
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