# Charge/Mass Ratio of Electron and Induction?

1. The electron moves in a circle of radius r = 0.051 cm. The magnetic field B = 0.64 T. Determine the speed of the electron. How many times is the speed of the electron smaller than the speed of light c = 3.0 * 10^8 m/s?

mass of electron = 9.1 x 10-31 kg

charge of electron = 1.6022*10-19 C

2. The magnetic field due to Earth is approximately equal to 0.5*10^-4 T. What current is required in Helmholtz coils used in the lab to produce magnetic field at least ten times larger than the magnetic field due to earth?

Use equation: B = 10.27*10^-4 x I

I is the current

### 1 Answer

- RealProLv 79 months agoBest Answer
Uhhhhhhhh

Magnetic force = centripetal force?

Bvq = mv^2 / r

v = rBq / m

r = 5.1×10^-4 m

2.

If I is "the current" and B is "the magnetic field", then the constant needs to include units

B = (10.27×10^-4 T/A) * I

Just some small details that are important.