Two toroids $1$ and $2$ have total number of tums $200$ and $100 $ respectively with average radii $40\; \mathrm{cm}$ and $20 \;\mathrm{cm}$ respectively. If they carry same current $i,$ the ratio of the magnetic flelds along the two loops is

A proton is moving along $Z$-axis in a magnetic field. The magnetic field is along $X$-axis. The proton will experience a force along

An electron is projected with uniform velocity along the axis inside a current carrying long solenoid. Then :

A charge particle of charge $q$ and mass $m$ is accelerated through a potential diff. $V\, volts$. It enters a region of orthogonal magnetic field $B$. Then radius of its circular path will be

At $t$ = $0$, a positively charged particle of mass $m$ is projected from the origin with velocity $u_0$ at an angle $37^o $ from the $x-$axis as shown in the figure. A constant magnetic field ${\vec B_0} = {B_0}\hat j$  is present in space. After a time interval $t_0$ velocity of particle may be:-

$OABC$ is a current carrying square loop an electron is projected from the centre of loop along its diagonal $AC$ as shown. Unit vector in the direction of initial acceleration will be