Physics questions ( not math )?

Question

1. Satellite ground operators use the feedback from a device called magnetometer, which senses the direction of Earth's magnetic field, to decide which torque coil to activate. what direction will the magnetometer read for earth's magnetic field whrn the satellite passes over earth's equator.

2. In order to protect other equipment, the body of a satellite must remain unmagnetized, even when the torque coils have been activated. Would hard or soft magnetic materials be best for building the rest of the satellite?

Answer 1

Earth's magnetic field is depicted as lines of force (the field) emerging straight up from one pole, bending vertically back around towards the other pole, following the curvature (more or less) of the planet, and bending back down towards the Earth as they near the pole at the other end.

The pointers on your satellite will continually align themselves with these lines of force. Thus, near either pole, the pointers will point downward, toward the Earth. Near the equator, they will point more or less horizontally, parallel to the Earth.

Magnetism is just 1/2 of the electro-magnetic force. So, to shield everything but your torque coils from the effects of passing through a magnetic field, you satellite should be made of material that will not conduct electricity. That will harden the satellite against the magnetism and the current passing through it would create. That results, because if the satellite can conduct electricity, there will be current generated throughout as it passes through the magnetic field...it will be like a generator coil passing through magnetic field to create electricity.

Answer 2

It took me a while to deduce that the magnetometer is on the satellite rather than the ground station. Over the Equator, the earth's magnetic field is approximately (but not exactly) horizontal, pointing toward the north magnetic pole (in northern Canada) and the south magnetic pole (which is near, but not at, the antipodal point). The satellite should be made of soft magnetic material, or ideally of nonmagnetic materials.