Question

The velocity of a helium nucleus travelling in a curved path in a magnetic field is $V$. The velocity of a proton moving in the same curved path in the same magnetic field is :

• A. $V$
• B. $4V$
• C. $2V$
• D. $V/2$

Answer 1

The correct option is C $2V$

Charge on helium nucleus $=2\alpha$
Mass of a helium nucleus $=4\beta$
Where $\alpha$ and $\beta$ are charge and mass of the helium nuclei respectively.
According to question,
$V=\frac{Bqr}{m}=\frac{2B\alpha r}{4\beta }$ ------------------- (I)
For proton:
Velocity $=\frac{B\alpha r}{\beta }=2V$ [From (I)]
Velocity of proton $=2V$