Question

A proton and an electron both moving with the same velocity $\upsilon$ enter into a region of magnetic field directed perpendicular to the velocity of the particles. They will now move in circular orbits such that

• A. their time periods will be same
• B. the time period for proton will be higher
• C. the time period for electron will be higher
• D. their orbital radii will be same

Answer 1

Answer: (B)

Time period of revolution, $T=\frac{2\pi m}{qB}$
Since $q$ and $B$ are the same for both proton and electron
$\therefore T\propto m$
As mass of proton is greater than mass of an electron, therefore
$T_p>T_c$