Why doesn't the Earth's magnetic field affect electronics? Why doesn't the Earth's magnetic field affect electronics in the same way that a magnetic field affects/exerts a force on a wire with a charge at a perpendicular angle? Isn't that why electric motors work? 
 A: Well, it does. The Earth's magnetic field is about half a gauss, or $0.5\times10^{-4}\rm\,T$.  So if you have a meter of wire carrying one ampere of current from east to west, it'll feel a magnetic force of $0.5\times10^{-4}\rm\,N$ in some mixture of upwards and the north-south direction that depends on the tilt of Earth's field at your location.  (I'm in the US Southeast and the field is about 70° from the horizontal, so if I did the experiment the force would be mostly to the north.)  That force corresponds to the weight $mg$ of an object with mass $m=5\rm\,mg$, which is pretty small compared to any real one-meter wire that wouldn't melt under an ampere of current.  Furthermore, most mains current is rapidly alternating, and most current carriers are cables which have both the supply and return currents right next to each other, which are both effects that make it harder to measure the force.
Earth's magnetic field can be a big annoyance if you're designing or using an instrument where free charges move and their exact trajectories matter, like a photomultiplier or a cathode-ray tube.
A: Earth's magnetic field is just too weak. half a gauss is nothing compared to your standard refridgerator magnet.
A: Actually, the Earth's magnetic field does affect electronics, probably, in a positive way, as it protects it from the effects of cosmic rays.
