Conclusion 1) In the apparatus that you used, why do the electrons go around in

Question

Conclusion 1) In the apparatus that you used, why do the electrons go around in a circle? (10 points) 2) One of the important ideas to take away from this lab is that magnetic fields trap charged particles. In other words, if a charged particle is moving along in a straight line and a magnetic field is suddenly turned on (or perhaps it enters a region with a magnetic field), the particle will circle around the B-field lines. With this in mind, look up and explain why an aurora happens. (20 points)

Explanation / Answer

Part 1)

From F = qvB, the velocity is perpendicular to the magnetic filed and the B field applies a force on them. The force always acts perpenidcularly to the direction of the velocity, which is the definitial of centripetal force. Since the force is centripetal, the charges are traveling in circles.

Part 2)

Auroras happen as the charged particles in the plasma in the upper atmosphere travel in spirals around the Earth's magnetic Field lines from the South to North pole. Near the poles, where the lines are concentrated, the spirals get tighter, and since the force has been applied for a long time, the charges are accelerated to quite high speeds. At these large speeds, the charged plasma particles collide with other gas molecules in the atmosphere causing them to give off light in the collision (conservation of energy). The release of the light is the aurora.

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