NEET Practice Questions (MCQs) with Answers & Solutions

If θ1 and θ2 are the apparent angles of dip observed in two vertical planes at right angles, the true angle of dip θ is given by cot^2 θ = cot^2 θ1 + cot^2 θ2. This relation is derived from the vector addition of the horizontal and vertical components of the Earth's magnetic field.

(d) As we know the relation between the magnetic permeability and susceptibility of material i.e.

                                    ${\mathrm{\mu }}_{\mathrm{r}}=1+{\mathrm{x}}_{\mathrm{m}}$    ...(i)

so, For diamagnetic substances, ${\mathrm{\mu }}_{\mathrm{r}}<1$

so, according to equation (i), the magnetic susceptibility (${\mathrm{x}}_{\mathrm{m}}$) of diamagnetic substance will be negative.

While in case of para and ferromagnetic substances, magnetic susceptibility is positive.

It will stay in any position at geomagnetic north and south poles.

In this case, work done

$$\begin{gathered} \mathrm{W}=\mathrm{MB}({\mathrm{cos\theta }}_1-{\mathrm{cos\theta }}_2) \\ =\mathrm{MB}(\cos 0°-\cos 60°) \\ =\mathrm{MB}\left(1-\frac{1}{2}\right)=\frac{\mathrm{MB}}{2} \\ \mathrm{MB}=2\sqrt{3}\mathrm{J} (\mathrm{so}, \mathrm{given} \mathrm{W}=\sqrt{3}\mathrm{J}) \\ \mathrm{\tau }=\mathrm{MB} \sin 60°=\left(2\sqrt{3}\right)\left(\frac{\sqrt{3}}{2}\right)\mathrm{J}=3\mathrm{J} \end{gathered}$$

Paramagnetic material will be feebly attracted, diamagnetic material will be feebly repelled and Ferromagnetic material will be strongly attracted. 

We know that 

      $U=-MB \cos \mathrm{\theta }$

   For stable equilibrium $\mathrm{\theta }=0°$

   So, $U=-MB$

            =$-(0.4)(0.16)=-0.064 \mathrm{J}$

Time period in vibration magnetometer

             T=2$\mathrm{\pi }$$\sqrt{\frac{I}{M\times B_H}}$

$\Rightarrow$       T$\propto$$\frac{1}{\sqrt{B_H}}$

$\Rightarrow$       $\frac{T_1}{T_{2_{}}}$=$\sqrt{\frac{(B_H{)}_2}{(B_H{)}_1}}$

$\Rightarrow$       $\frac{2}{T_2}$=$\sqrt{\frac{6}{24}}$

             T = 4s

Electromagnetics is made of soft iron because soft iron has low retentivity and low coercive force or low coercivity. Soft iron is a soft magnetic material.

Atoms which have paired electrons have the magnetic moment zero. Because diamagnetism is the intrinsic property of every material and it is generated due to mutual interaction between the applied magnetic field orbital motion of electrons.

So, the magnetic moment of a diamagnetic atom is equal to zero.

Diamagnetic substance are weekly magnetised in a direction opposite to that of applied magnetic field. These are repelled in an external magnetic field i.e., have a tendency to move from high to low field region.