The Bar Magnet

The magnetic moment of a circular orbit of radius 'r' carrying a charge 'q' and rotating with velocity v is given by

If $r$ is the orbital radius and $v$ is the orbital velocity of an electron in a hydrogen atom, then its magnetic dipole moment is

A short bar magnet has a magnetic moment of$0.65 \mathrm{J} {\mathrm{T}}^{-1}$ then the magnitude and direction of the magnetic field produced by the magnet at a distance $8 \mathrm{cm}$ from the centre of magnet on the axis is

The characteristics of two coils are given below:

If the magnetic moments of both coils $A$ and $B$ are equal, choose the correct relation.

When a magnetic needle kept in a non-uniform magnetic field 

What is magnetic moment?

A thin uniform ring of mass m and electric charge $Q$ uniformly distributed rotates around an axis perpendicular to its plane and going through its centre. The angular momentum of the ring is $7.5\times {10}^{-4} \mathrm{kg} \mathrm{m} {\mathrm{s}}^{-2}$. The ring is in a homogeneous magnetic field of a field strength of $0.1\mathrm{T}$ and the lines of the magnetic induction are parallel with the plane.

The magnetic field strength of a bar magnet at a point P along its axial line is $B$. If the distance between the centre and point P is halved the new magnetic field strength at P is $B\text{'}$. Find the relation between $B$ and $B\text{'}$.

The force experienced by a magnetic pole of strength $m$ kept at a distance of $d$ from the center of a short magnet of magnetic moment $M$ on its equatorial line is

Assertion: The magnetic field lines are continuous and form closed loops.

Reason: Magnetic monopole does not exist.

The correct option among the following is

A planet has magnetic dipole moment of $27\times {10}^{22} \mathrm{A} {\mathrm{m}}^2$. If the radius of the planet is $300 \mathrm{km}$, what would be the magnetic field at its equator?
$\left(\text{Take}, \frac{\mu }{4\pi }={10}^{-7}\right)$

A short bar magnet of magnetic moment $0.05 \mathrm{J} {\mathrm{T}}^{-1}$ is placed with its axis perpendicular to the earth's field direction. The resultant field is inclined at $45°$ with earth's field on its axis at a distance of $5.0 \mathrm{cm}$ from the center of the magnet. The magnitude of earth's field at this point is
(Take $\frac{\mu }{4\pi }={10}^{-7}\mathrm{SI}$ unit)

Calculate the, magnetic induction or magnetic field) at a point $1Å$ away from a proton, measured along its axis of spin. The magnetic moment of the proton is $1.4\times {10}^{-26} \mathrm{A}-{\mathrm{m}}^2$.

A thin bar magnet of length $L$ and magnetic moment $M$ is bent at the midpoint so that the two parts are at right angles. The new magnetic length and magnetic moment are respectively

An $\mathrm{L}$ shaped bar magnet is converted into a straight bar magnet. It is found that the change in the magnetic moment is $40\%$. The original shape of the bar magnet was-

Here it is known to us that $y>x$. Later the shape of the bar magnet is like this

Calculate the ratio $\frac{y}{x}$.

What is the magnitude of the equatorial fields due to a bar magnet of length $5.0 \mathrm{cm}$ at a distance $75 \mathrm{cm}$ from its mid point? The magnetic moment of the bar magnet is $0.75 \mathrm{A} {\mathrm{m}}^2$.

The neutral points on the equatorial line were found to be at $0.2 \mathrm{m}$ from the centre of a short-bar magnet. The horizontal component of earths magnetic field induction is $0.39\times {10}^{-4}$Tesla. If ${\mu }_0=4\pi \times {10}^{-7}$ Henry/$\mathrm{m}$, the magnetic moment of the short-bar-magnet is

The intensity of magnetic field at a point $X$ on the axis of a small magnet is equal to the field intensity at another point $Y$ on equatorial axis. The ratio of distance of $X$ and $Y$ from the centre of the magnet will be

A bar magnet is oscillating in a magnetic field and its frequency is $10 \mathrm{Hz}$. If another identical piece of brass be placed over that magnet, the frequency of that combination in that field is

A long bar magnet of time period $\mathrm{T}$ is cut into four equal parts by cutting it perpendicular to both length and breadth. The time period of each part is