On p.809 of Weidner and Sells, Elementary Classical Physics, Allan and
Bacon, Boston (1965, which was my seventh wife's undergraduate physics
text ... (She married me to get an A in that course.) ... we read, "At
the equator the Earth's magnetic field is horizontal (?), toward the
North, and has a magnitude of 0.70 gauss." ... Ooooh, you'll like the
questions: (a) In what direction, East or West, should a proton be fired
to encircle the Earth at constant speed? (b) What is the proton's speed?
(c) Kinetic energy? (d) Is the gravitational force significant here?
[It is if I'm there.] and (e) which oil is preferable in prewar cars
with more than 40,000 miles on them: Valvoline or Quaker State? And
where do you think you're going anyway? [This is a lot of work; I hope
you appreciate it.] "At some location in the northern hemisphere on
Earth [whew], the magnitude of the Earth's magnetic field is 0.25 gauss
and the dip angle, the angle between the direction of the field lines and
the horizontal (pointing north), is 70 degrees. A compass points to
geographic north at this location. What is the magnetic flux through an
area of 1.0 m^2 in the horizontal plane?
There's more, but no more gauss. Some stuff about field lines, which
must be the E & M version of caloric (just kidding).