The Earth's magnetic field is approximately

  • A. 5 tesla
  • B. 50 microtesla
  • C. 50 millitesla
  • D. zero at the equator

Explanation

At around 50 microtesla the geomagnetic field is weak enough that a compass needle needs to be delicately mounted to respond to it, and strong enough to deflect charged particles from the Sun. The field is horizontal near the magnetic equator and dips steeply near the poles. A laboratory electromagnet is thousands of times stronger.

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