An infinitely long straight conductor carries a current of 5A as shown. An electron is moving with a speed of 10⁵ m/s parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. Calculate the magnitude of the force experienced by the electron at that instant.

A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is :
$$\left( {{\mu _0} = 4\pi \times {{10}^{ - 7}}Tm{{A}^{-1}}} \right)$$

A cylinderical conductor of radius R is carrying a constant current. The plot of the magnitude of the magnetic field. B with the distane d from the centre of the conductor, is correctly represented by the figure :

Ionized hydrogen atoms and $$\alpha $$-particles with same momenta enters perpendicular to a constant magnetic field, B. The ratio of their radii of their paths r_H : r_{$$\alpha $$} will be :