Two charged particles, having same kinetic energy, are allowed to pass through a uniform magnetic field perpendicular to the direction of motion. If the ratio of radii of their circular paths is $6: 5$ and their respective masses ratio is $9: 4$. Then, the ratio of their charges will be.

An electron moving with a velocity ${\vec V_1} = 2\,\hat i\,\, m/s$ at a point in a magnetic field experiences a force ${\vec F_1} =  - 2\hat j\,N$ .  If the electron is moving with a velocity ${\vec V_2} = 2\,\hat j \,\,m/s$ at the same point, it experiences a force ${\vec F_2} =  + 2\,\hat i\,N$ .  The force the electron would experience if it were moving with a velocity ${\vec V_3} = 2\hat k$  $m/s$ at the same point is

Which of the following statement is correct :

Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius $R$ with constant speed $v$. The time period of the motion

Ratio of electric and magnetic field due of moving point charge if its speed is $4.5 \times 10^{5} \;m / s$

Two ions having masses in the ratio $1 : 1$ and charges $1 : 2$ are projected into uniform magnetic field perpendicular to the field with speeds in the ratio $2 : 3$. The ratio of the radii of circular paths along which the two particles move is