Question 3

Cosmic rays (charged particles from space) strike the earth more frequently at the poles than at the equator. Which of the following is the best explanation for this fact?
[Hint: Consider the forces acting on charged particles traveling on paths directed toward the center of the earth.]

• A. The magnetic force on the charged particles is strongest at the poles and pulls the particles into the Earth.
• B. The direction of the magnetic field at the poles is such that there is little or no magnetic force to deflect the particles away from Earth.
• C. The magnetic field lines at the equator are pointed opposite to the velocity vectors of the charged particles, pushing them back into space.
• D. The magnetic force on the charged particles in weakest at the equator and cannot overcome the electrostatic repulsion forces.
• E. The magnetic repulsion forces at the poles just balance the electrostatic attraction, so that gravity takes over and pulls the charged particles to Earth.

Formula Sheet

Question 2

Question 4

Up to Unit 12 Table of Contents