Question 1

The SI unit of magnetic dipole moment is:

Accepted Answer

The magnetic dipole moment $M$ is given by the product of current and area ($M = I \cdot A$). The SI unit of current is Ampere (A) and area is square meter ($	ext{m}^2$). Therefore, the SI unit of magnetic dipole moment is Ampere-meter squared ($	ext{A m}^2$). It is also equivalent to Joule per Te

Question 2

The magnetic lines of force inside a bar magnet are:

Accepted Answer

Inside a bar magnet, the magnetic field lines run from the south pole to the north pole. This is necessary to form continuous closed loops, unlike electric field lines which do not form closed loops.

Question 3

The magnetic susceptibility ($\chi$) of a perfect diamagnetic substance is:

Accepted Answer

For a perfect diamagnetic substance, the magnetic susceptibility is $\chi = -1$. This is because diamagnetic materials completely expel magnetic field lines from their interior, making the relative permeability $\mur = 0$, and since $\chi = \mur - 1$, it results in $-1$.

Question 4

Curie's law states that the magnetic susceptibility of a paramagnetic substance is inversely proportional to its:

Accepted Answer

According to Curie's law, the magnetic susceptibility $\chi$ of a paramagnetic material is inversely proportional to its absolute temperature $T$, expressed as $\chi = C/T$ where $C$ is Curie's constant.

Question 5

At the magnetic poles of the Earth, the angle of dip is:

Accepted Answer

At the magnetic poles of the Earth, the Earth's magnetic field is completely vertical. Therefore, the angle made by the total magnetic field vector with the horizontal is $90^\circ$.

Magnetism and Matter — NCERT Class 12 Physics Important Questions & Revision Notes