A particle of charge e and mass m moves with a velocity v in a magnetic field B applied perpendicular to the motion of the particle. The radius r of its path in the field is

• $\frac{\mathrm{mv}}{\mathrm{Be}}$

• $\frac{\mathrm{Be}}{\mathrm{mv}}$

• $\frac{\mathrm{ev}}{\mathrm{Bm}}$

• $\frac{\mathrm{Bv}}{\mathrm{em}}$

32.

A neutron, a proton, an electron and an α-particle enter a region of uniform magnetic field with the same velocities. The magnetic field is perpendicular and directed into the plane of the paper. The tracks of the particles are labelled in the figure. The electron follows the track.

         

• A

• B

• C

• D

The deflection in a moving coil galvanometer is reduced to half when it is shunted with a 40 Ω coil. The resistance of the galvanometer

• 80 Ω

• 40 Ω

• 20 Ω

• 15 Ω

A current of $\left(\frac{2}{\sqrt{3}}\right)$ A, produces a deflection of 60° in a tangent galvanometer. The reduction factor is

• $\left(\frac{2}{\sqrt{3}}\right) \mathrm{A}$

• $\left(\frac{2}{3}\right) \mathrm{A}$

• 2 A

• $\left(\frac{3}{2}\right) \mathrm{A}$

In an AC circuit, V and I are given by V = 150 sin (150 t) volt and $\mathrm{I} = 150 \sin \left(150 + \frac{\mathrm{\pi }}{3}\right)$ amp. The power dissipated in the circuit is

• 106 W

• 150 W

• 5625 W

• Zero

In the series L-C-R circuit shown, the impedance is

• 200 Ω

• 100 Ω

• 300 Ω

• 500 Ω

The energy stored in an inductor of self inductance L henry carrying a current of I ampere is

• $\frac{1}{2} {\mathrm{L}}^2\mathrm{I}$

• $\frac{1}{2} {\mathrm{LI}}^2$

• LI²

• L²I

A transformer works on the principle of

• self-induction

• electrical inertia

• mutual induction

• magnetic effect of the electrical current

Flash spectrum confirms a/an

• total solar eclipse

• lunar eclipse

• earthquake

• magnetic storm

Wavelength of given light waves in air and in a medium are 6000 $\stackrel{\circ }{\mathrm{A}}$ and 4000 $\stackrel{\circ }{\mathrm{A}}$ respectively. The critical angle is

• ${\tan }^{-1} \left(\frac{2}{3}\right)$

• ${\tan }^{-1} \left(\frac{3}{2}\right)$

• ${\sin }^{-1} \left(\frac{2}{3}\right)$

• ${\sin }^{-1} \left(\frac{3}{2}\right)$