Q. No.If a bar magnet is kept on a horizontal plane with N-pole of bar magnet facing geographic N-pole and S-pole of bar magnet facing geographic S-pole, then the number of neutral points is:
| 1. | 0 | 2. | 1 |
| 3. | 2 | 4. | Infinite |
| 1. | \(128\pi^2\) | 2. | \(50\pi^2\) |
| 3. | \(1280\pi^2\) | 4. | \(5\pi^2\) |
1. \(0.4~\text T\)
2. \(4~\text T\)
3. \(0.4~\text{mT}\)
4. \(4~\text{mT}\)
A current-carrying loop is placed in a uniform magnetic field in four different orientations, I, II, III & IV. The decreasing order of potential energy is:
| 1. | I > III > II > IV | 2. | I > II >III > IV |
| 3. | I > IV > II > III | 4. | III > IV > I > II |
A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in the equilibrium state. The energy required to rotate it by \(60^{\circ}\) is \(W\). Now the torque required to keep the magnet in this new position is:
1. \(\frac{W}{\sqrt{3}}\)
2. \(\sqrt{3} W\)
3. \(\frac{\sqrt{3} W}{2}\)
4. \(\frac{2 W}{\sqrt{3}}\)
A short bar magnet of magnetic moment \(0.4~\text {J/T}\) is placed in a uniform magnetic field of \(0.16~\text T.\) The magnet is in stable equilibrium when the potential energy is:
1. \(0.064~\text J\)
2. zero
3. \(-0.082~\text J\)
4. \(-0.064~\text J\)
A bar magnet of length \(l\) and magnetic dipole moment \(M\) is bent in the form of an arc as shown in the figure. The new magnetic dipole moment will be:
| 1. | \(\dfrac{3M}{\pi}\) | 2. | \(\dfrac{2M}{l\pi}\) |
| 3. | \(\dfrac{M}{ 2}\) | 4. | \(M\) |
| 1. | \(9~\text{gauss}\) | 2. | \(4~\text{gauss}\) |
| 3. | \(36~\text{gauss}\) | 4. | \(4.5~\text{gauss}\) |
| 1. | \(M\) | 2. | \(\dfrac{M\pi}{2}\) |
| 3. | \( \dfrac{M}{2\pi}\) | 4. | \(\dfrac{2M}{\pi}\) |
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