A particle with charge $+Q$ and mass m enters a magnetic field of magnitude $B,$ existing only to the right of the boundary $YZ$. The direction of the motion of the $m$ particle is perpendicular to the direction of $B.$ Let $T = 2\pi\frac{m}{{QB}}$ . The time spent by the particle in the field will be 

A positively charged particle moving due east enters a region of uniform magnetic field directed vertically upwards. The particle will

An electron with energy $0.1\,ke\,V$ moves at right angle to the earth's magnetic field of $1 \times 10^{-4}\,Wbm ^{-2}$. The frequency of revolution of the electron will be. (Take mass of electron $=9.0 \times 10^{-31}\,kg$ )

Give definition of magnetic field and give its unit.

An electric field of $1500\, V/m$ and a magnetic field of $0.40\, weber/metre^2$ act on  a moving electron. The minimum uniform speed along a straight line the electron could  have is