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Hi All,

Having difficultly figuring out where I've gone wrong with this problem. Any guidance gratefully received.

1. Homework Statement

1. Homework Statement

A 4.76 keV electron (an electron that has a kinetic energy equal to 4.76 keV) moves in a circular orbit that is perpendicular to a magnetic field of 0.392 T.

i) Find the radius of the orbit.

**2. Homework Equations**

KE = 0.5 m v^2

r = mv / qB (where r = radius, m = mass of electron, q = charge of electron and B = magnetic field)

**3. The Attempt at a Solution**

Given the KE and the mass, find the velocity v. KE = 4.76 x 10^3 eV and m = 9.109x10^-31 kg

v = sqrt ( (2xKE / m))

v = sqrt ( (2x(4.76x10^3)/9.109 x 10^-31))

v= 1.02 x 10^17 m/s

Now having found the velocity v, find the radius r.

r = mv / qB

r = (9.109x10^-31)(1.02 x 10^17) / (1.602x10^-19)(0.392)

r = 1.48 x 10^6 m

However this answer is wrong and I don't know where I'm going wrong. Any help greatfully recieved.