The contribution of ampere What contribution does ampere make to physics, chemistry and mathematics~

The contribution of ampere What contribution does ampere make to physics, chemistry and mathematics~

Andre Marie amp è (1775-1836), a French physicist, was born in a wealthy family in Lyon on January 22, 1775

On the ground of the northern hemisphere, if there is a long straight wire horizontally placed in the east-west direction and there is a current from west to East, the direction of the force exerted by the geomagnetic field on the wire should be
[ ]
A. Up by North
B. Down south
C. Vertical up
D. Vertical down
Why not C?

In the northern hemisphere, the magnetic line of the earth's magnetic field tends to be higher in the South and lower in the north

I would like to ask about how the palm and the back of the hand are converted? When to use the palm and when to use the back of the hand

Ampere rule: 1. Judge the magnetic field around the electrified straight wire. 2. Judge the north and south pole of the electrified solenoid. 3. Judge the direction of the magnetic field of the ring current. Method: hold the electrified wire with the right hand and make the direction of the straight thumb consistent with the direction of the current. Then, the direction of the curved four fingers is