Magnetism and Matter

Iron is ferromagnetic

• at all temperatures

• at NTP only

• above 770°C

• below 770°C

Relative permeability of iron is 5500, then its magnetic susceptibility will be

• 5500 × 10⁷

• 5500 × 10^-7

• 5501

• 5499

In the unmagnetized state magnetic domains of a magnetic substance are oriented at

• 60°

• 90°

• randomly

• 150°

When a ferromagnetic material is heated above its Curie temperature it

• gets demagnetised

• becomes diamagnetic

• behaves like a paramagnetic substance

• remains unaffected

A hydrogen atom is paramagnetic. A hydrogen molecule is

• diamagnetic

• paramagnetic

• ferromagnetic

• none of these

A bar magnet of magnetic moment $\overrightarrow{\mathrm{M}}$ is placed in the magnetic field $\overrightarrow{\mathrm{B}}$. The Torque acting on the magnet is :

• $\overrightarrow{\mathbf{M}} \times \overrightarrow{\mathbf{B}}$

• $\overrightarrow{\mathbf{M}} - \overrightarrow{\mathbf{B}}$

• $\frac{1}{2}\overrightarrow{\mathbf{M}} \times \overrightarrow{\mathbf{B}}$

• $\overrightarrow{\mathbf{M}} + \overrightarrow{\mathbf{B}}$

At a certain place, magnitude of horizontal and vertical components of a magnetic field are same. The total intensity of magnetic field at that place will be

• H

• H²

• 2H

• $\sqrt{2 } \mathrm{H}$

The magnetic lines of force inside a bar magnet

• are from north-pole to south-pole of the magnet

• do not exist

• depend upon the area of cross-section of the bar magnet

• are from south-pole to north-pole of the magnet

Curie temperature is the temperature above which

• a ferromagnetic material becomes paramagnetic

• a paramagnetic material becomes diamagnetic

• a ferromagnetic material becomes diamagnetic

• a paramagnetic material becomes ferromagnetic

Which one of the following is ferromagnetic?

• Gold

• Wood

• Manganese

• Nickle