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 particle of mass $'m'$ and carrying a charge $'q'$ enters with a velocity $'v'$ perpendicular to a uniform magnetic field. The time period of rotation of the particle

A charge particle of $2\,\mu\,C$ accelerated by a potential difference of $100\,V$ enters a region of uniform magnetic field of magnitude $4\,m\,T$ at right angle to the direction of field. The charge particle completes semicircle of radius $3\,cm$ inside magnetic field. The mass of the charge particle is $........\times 10^{-18}\,kg$.

The figure shows three situations when an electron moves with velocity $\vec v$ travels through a uniform magnetic field $\vec B$. In each case, what is the direction of magnetic force on the electron

An electron emitted by a heated cathode and accelerated through a potential difference of $ 2.0 \;kV$, enters a region with uniform magnetic field of $0.15\; T$. Determine the trajectory of the electron if the field

$(a)$ is transverse to its initial velocity,

$(b)$ makes an angle of $30^o$ with the initial velocity

An electron enters a region where electrostatic field is $20\,N/C$ and magnetic field is $5\,T$. If electron passes undeflected through the region, then velocity of electron will be.....$m{s^{ - 1}}$