1. An electron in the Earth’s atmosphere has a charge of = 1.6 × 1019 C and a ve

Question

1. An electron in the Earth’s atmosphere has a charge of  = 1.6 × 1019 C and a velocity of  =7.50 × 106 m/s perpendicular to the Earth’s magnetic field at an altitude where the magnitude of themagnetic field is 1.0 × 105 T. What is the radius of the path the electron follows? Show your work.

2. You have landed a great summer job in the medical school assisting in a research group investigating
short lived radioactive isotopes which might be useful in fighting cancer. Your group is working on a wayof transporting alpha particles (Helium nuclei) from where they are made to another room where theywill collide with other material to form the isotopes. Since the radioactive isotopes are not expected tolive very long, it is important to know precisely how much time it will take to transport the alphaparticles. Your job is to design that part of the transport system which will deflect the beam of alphaparticles (m = 6.64 x 10-27 kg, q = 3.2 x 10-19 C) through an angle of 90o by using a magnetic field. Thebeam will be traveling horizontally in an evacuated tube. At the place the tube is to make a 90o turn youdecide to put a dipole magnet which provides a uniform vertical magnetic field of 0.030 T. Your designhas a tube of the appropriate shape between the poles of the magnet. Before you submit your designfor consideration, you must determine how long the alpha particles will spend in the uniform magneticfield in order to make the 90o-turn.

3. A particle with a charge of +8.4 C and a speed of 40 m/s enters a uniform magnetic field whosemagnitude is 0.33 T. For each of the three cases in the drawing, calculate the magnitude and direction ofthe magnetic force on the particle.

Explanation / Answer

electron charge e = 1.6 × 1019 C

velocity v = 7.50 × 106 m/s

Mass of electron m = 9.11 x10 -31 kg

magnitude of the magnetic field B = 1.0 × 105 T

the radius of the path the electron r = ?

In magnetic field , Bve = mv 2/ r

Be = mv / r

From this r = mv / Be

= ( 9.11 x10 -31)(7.50 × 106 )/( 1.0 × 105 )(1.6 × 1019)

= 4.27 m

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