# How many elementary charges does this particle carry?

1. A force of 9.2x10-14 acts on an unknown particle that travels at 2.40x106 m/s into a magnetic field of 4.8x10-2 T. How many elementary charges does this particle carry?
I've used Fm=qvB and found q=Fm/vB and got an answer of q=7.986 x10-19 C. I'm not sure where to go from here. I assume I have to divide by the elementary charge... but I don't know what that is. Haha.

2. An alpha particle with a charge of 3.20x10-19 C and a mass of 6.65 x10-27 kg is travelling at 5.0 x106 m/s. When it enters a magnetic field of 6.4 x10-2 T, a magnetic force provides the centripetal force for the alpha particle. The centripetal force causes the alpha particle to travel in a circular path. Calculate the radius of the circular path.
Do I simply use the equation r=(mv)/(qB)?

Hootenanny
Staff Emeritus
Gold Member
1. A force of 9.2x10-14 acts on an unknown particle that travels at 2.40x106 m/s into a magnetic field of 4.8x10-2 T. How many elementary charges does this particle carry?
I've used Fm=qvB and found q=Fm/vB and got an answer of q=7.986 x10-19 C. I'm not sure where to go from here. I assume I have to divide by the elementary charge... but I don't know what that is. Haha.

The elementary charge is the same as the magnitude of the charge of an electron, about 1.602×10-19 C.
2. An alpha particle with a charge of 3.20x10-19 C and a mass of 6.65 x10-27 kg is travelling at 5.0 x106 m/s. When it enters a magnetic field of 6.4 x10-2 T, a magnetic force provides the centripetal force for the alpha particle. The centripetal force causes the alpha particle to travel in a circular path. Calculate the radius of the circular path.
Do I simply use the equation r=(mv)/(qB)?

Sounds good to me Last edited:
dx
Homework Helper
Gold Member
1. the charge on an electron is -1.602 176 487 × 10–19 C

2. Yes, thats the correct formula.

Thanks! 