# Two small bar magnets are placed in the air at a distance r apart. The magnetic force between them is proportional to: (1) ${r}^{2}$ (2) ${r}^{-2}$ (3) ${r}^{-3}$ (4) ${r}^{-4}$

Subtopic:  Analogy between Electrostatics & Magnetostatics |
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A short magnetic dipole is placed at the origin with its dipole movement directed along the +x-axis. If magnetic field induction at a point P (r, 0) is $$B\hat{i}$$, the magnetic field induction at point Q (0, 2r) will be:

1. $$-\frac{B}{16}\hat{i}$$

2. $$-\frac{B}{8}\hat{j}$$

3. $$\frac{B}{16}\hat{j}$$

4. $$-\frac{B}{16}\hat{j}$$

Subtopic:  Bar Magnet |
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Oersted is a unit of :

(1) Dip

(2) Magnetic intensity

(3) Magnetic moment

(4) Pole strength

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Magnetic field lines

1. Cannot intersect

2. Are always closed curves

3. Can pass through vacuum

4. All of these

Subtopic:  Magnetic Field & Field Lines |
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The unit of pole strength is:

1. $A{m}^{2}$

2. Am

3. $\frac{{A}^{2}}{m}$

4. $\frac{{A}^{2}}{{m}^{2}}$

Subtopic:  Bar Magnet |
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A small bar magnet is placed with its north pole facing the magnetic north pole. The neutral points are located at a distance r from its centre. If the magnet is rotated by 180o, the neutral point shall be obtained at a distance of:
1. $$2r$$
2. $$\sqrt{2}r$$
3. $$2^{\frac{1}{3}}r$$
4. $$\frac{r}{2\sqrt{2}}$$

Subtopic:  Earth's Magnetism (OLD NCERT) |
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A bar magnet of length l and magnetic dipole moment M is bent to form an arc which subtends an angle of $120°$ at centre. The new magnetic dipole moment will be

1.  $\frac{3\mathrm{M}}{2\mathrm{\pi }}$

2.  $\frac{3\sqrt{3}\mathrm{M}}{2\mathrm{\pi }}$

3.  $\frac{3\mathrm{M}}{\mathrm{\pi }}$

4.  $\frac{2\mathrm{M}}{\mathrm{\pi }}$

Subtopic:  Bar Magnet |
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The magnetic field at a point x on the axis of a small bar magnet is equal to the field at a point y on the equator of the same magnet. The ratio of the distances of x and y from the centre of the magnet is:
1. ${2}^{-3}$

2. ${2}^{-1}{3}}$

3. ${2}^{3}$

4. ${2}^{1}{3}}$

Subtopic:  Bar Magnet |
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A magnet of magnetic moment 20 C.G.S. units are freely suspended in a uniform magnetic field of intensity 0.3 C.G.S. units. The amount of work done in deflecting it by an angle of ${30}^{o}$ in C.G.S. units is
(1) 6

(2) $3\sqrt{3}$

(3) $3\left(2-\sqrt{3}\right)$

(4) 3

Subtopic:  Analogy between Electrostatics & Magnetostatics |
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The magnetic field due to a short magnet at a point on its axis at a distance X cm from the middle point of the magnet is 200 Gauss. The magnetic field at a point on the neutral axis at a distance of X cm from the middle of the magnet is:

1. 100 Gauss

2. 400 Gauss

3. 50 Gauss

4. 200 Gauss

Subtopic:  Analogy between Electrostatics & Magnetostatics |
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