Test: Magnetism and Matter - 3 - CUET Humanities MCQ

The relative permeability of iron is of the order 10³ as the relative permeability of ferromagnetic materials is very large.

Diamagnetic materials are repelled by the magnetic field.

Magnet is a material which has the capability of attracting the iron pieces. Strength of a magnet is maximum at its poles and strength of the magnet is minimum in the middle of the magnet.

If a bar magnet of pole strength q and magnetic moment m is divided into two equal pieces by cutting it perpendicular to its length, then q remains the same, but m is halved as the length of the magnet becomes half of the original value. This is because magnetic moment is the product of the pole strength and the separation between the poles.

When a ferromagnetic material is heated above its Curie temperature, the thermal motions at a high temperature destroy its magnetism and the material behaves as a paramagnet.

The permeability of a paramagnetic substance is greater than unity, which means it is larger than the permeability of free space.

The SI unit of magnetic dipole moment is ampere metre² (A m²). The magnetic dipole moment is a measure of the strength of a magnetic dipole, which is a magnetic field produced by a current loop or a permanent magnet. It is calculated by multiplying the current flowing through the loop by the area of the loop.

Earth's magnetism was discovered by William Gilbert. He was an English physician and natural philosopher who conducted extensive experiments and observations on magnetism.

Torque acting on a magnet when it is rotated by θ° from its equilibrium position is MB sin θ which is equivalent to .

The magnetic dipole moment is a vector quantity. The direction of magnetic dipole moment is from south pole to north pole of a bar magnet.

Magnetic susceptibility of ferromagnetic substance is positive in nature and its magnitude is very very greater than 1.

Magnetic lines of force in a bar magnet are continuous forming closed loops as shown in the figure.
Outside the magnet, the lines run from north pole to south pole, whereas oppositely inside.

When a bar magnet is suspended freely, it aligns itself in the north-south direction due to the influence of the earth's magnetic field. This behaviour indicates that the earth itself behaves as a magnet, with its magnetic field lines oriented from the magnetic north pole to the magnetic south pole. The absence of isolated magnetic poles on the earth is another indicator of its magnetic behaviour.

At poles, the angle of dip will be 90° because the earth's magnetic field will be almost vertical there.

Ferrites are generally electrically insulating materials, meaning they have low conductivity. This property makes them useful for applications where electrical insulation is required.

The magnetic lines of force due to a bar magnet are closed loops. The field lines are directed from the north pole to the south pole outside the magnet. The field lines are directed from the south pole to the north pole inside the magnet.

Clearly, the magnetic field above the wire carrying current from west to east is from north to south.

The neutral point in the magnetic field of a horizontally placed bar magnet is a point where the magnetic field due to that bar magnet is equal to earth's horizontal magnetic field.

The earth's magnetic field is believed to be generated by electric currents in the conductive material of its core, created by convection currents due to heat escaping from the core. The magnetic field of earth is due to motion and distribution of some material in and outside the earth.