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

  • 1 year ago
    Favorite Answer


    Magnetic force = centripetal force?

    Bvq = mv^2 / r

    v = rBq / m

    r = 5.1×10^-4 m


    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.

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