High above the surface of the earth, charged particles (such as electrons and protons) can become trapped in the earth's magnetic field in regions known as van allen belts. a typical electron in a van allen belt has an energy of 40 kev and travels in a roughly circular orbit with an average radius of 210 m. what is the magnitude of the earth's magnetic field where such an electron orbits?

What have we learned from fossil evidence about evolution? a) it is an abrupt change. b)the process is observable. c) it takes place during one lifetime only. d)the most complex traits are always selected.

What is it called when part of a cell membrane closes around a molecule to allow the molecule to enter the cell? a. passive transport b.diffusion c. endocytosis d. exocytosisc. endocytosis

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.