Quick questions on Magnetic fields and materials - TCE Physics (Tasmania)

A straight current-carrying wire produces a circular magnetic field around it, with strength $B = \dfrac{\mu_0 I}{2\pi r}$ that falls off with distance $r$ from the wire. The right-hand grip rule gives the direction: point your right thumb along the conventional current and your curled fingers show the field looping around the wire.

Because the field at a point is a vector, the total field from two or more wires is the vector sum of each wire's contribution. Find each magnitude with $B = \dfrac{\mu_0 I}{2\pi r}$ using its own distance, work out each direction with the grip rule, then add them as vectors. Between two parallel wires carrying current in the same direction the fields partly cancel, which is linked to the attractive force the wires exert on each other.

Earth behaves like a giant bar magnet tilted slightly from its spin axis. A compass aligns horizontally with this field, but a needle free to rotate vertically also tilts downward; the angle below the horizontal is the angle of dip. The dip is near zero at the equator and close to vertical near the magnetic poles, which tells us the field has a vertical component that varies with latitude.