Magnetism And Matter - Electromagnetism - Physics Previous Year Questions

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

The magnetic susceptibility of ferromagnetic materials is

The period of oscillation of a bar magnet at a place is 2 s . At the same place, the period of oscillation of another identical bar magnet whose magnetic moment is 4 times so that of first magnet is

The expression for the magnetic energy stored in a solenoid of length $L$, in terms of magnetic field $B$ and area $A$ is

materials suitable for permanent magnets, must have which of the following properties?

A bar magnet of magnetic moment $2 \mathrm{~A}-\mathrm{m}^2$ lies aligned with the direction of a uniform magnetic field of 0.3 T . The amount of work required by an external torque to turn the magnet so as to align its magnetic moment normal to the field direction is

If $\chi$ is the susceptibility and $\mu_r$ is the relative permeability of a ferromagnetic substance, then

Two short magnets of equal dipole moments $M$ are fastened perpendicularly at their centres which lies at origin. Let two magnets lie along $X$-axis and $Y$-axis, respectively.

The magnitude of the magnetic field at a distance $R$ from the centre on the $Y$-axis is $\frac{\mu_0}{4 \pi} \frac{M_0}{R^3}$. Assuming, $R \gg l$ (magnet length), the magnitude of $M$ is

If relative permeability of iron is 5500 , then its susceptibility is

The magnitude of axial field due to a bar magnet at a distance of 1 m , is found to be $5 \times 10^{-8} \mathrm{~T}$. The magnetic moment of the bar magnet is $\left(\mu_0=4 \pi \times 10^{-7}\right)$

A thin magnetic needle is placed in a magnetic field of 200 G with its axis at $30^{\circ}$ to the direction of the field. Find the magnetic moment of the needle, if it experiences a torque of 0.012 Nm in this field.

In the magnetic meridian of a certain place, the horizontal component of the earth's magnetic field is 86.6 G (Gauss) and the magnetic field of earth is 100 G (Gauss). The the dip angle is

An iron bar having a cross-sectional area of $2 \times 10^{-5} \mathrm{~m}^2$ and magnetising field of $2400 \mathrm{~A} / \mathrm{m}$ produce a magnetic flux $2.4 \pi \times 10^{-5} \mathrm{~Wb}$. What will be the value of permeability $\mu$ and susceptibility $\chi$ of the bar (given, $\mu_0=4 \pi \times 10^{-7}$ )

A solenoid has a core of a material with relative permeability $\frac{800}{\pi}$. The windings of the solenoid are insulated from the core and carry current of 2 A . If the number of turns is 1000 per metre, find the magnetic field $B$.

Let $m$ and $r$ are the dipole moment and radius of earth respectively. Then, the earth's magnetic field at the equator is

A short bar magnet placed with its axis at $30^{\circ}$ with an external field of 800 G experiences a torque of 0.016 Nm . The magnetic moment of the bar magnet is

Which of the following is desirable for making permanent magnets?