$$\alpha$$-particle is revolving in a circular path with radius $$r$$ with speed $$v$$, then find the value of magnetic dipole moment.
Assertion : Paramagnetic substances get poorly attracted in magnetic field.
Reason : Because magnetic dipoles are aligned along external magnetic field weakly.
The horizontal component of the earth's magnetic field at any place is $$0.36 \times 10^{-4} \mathrm{~Wb} / \mathrm{m}^2$$. If the angle of dip at that place is $$60^{\circ}$$, then the value of vertical component of the earth's magnetic field will be (in $$\mathrm{Wb} / \mathrm{m}^2$$ )
The angle of dip, if dip needle oscillating in vertical plane makes 40 oscillations per min in a magnetic meridian and 30 oscillations per minute in vertical plane at right angle to the magnetic meridian is