Question

How do we know electromagnetic force exists?

Answer 1

Magnets

Explanation:

The very existence of magnetized material in nature proves its existence.

But also, there exists "true north" and "magnetic north," a separation of 1.5 degrees.

True north refers to the axial point around which the earth turns either north or south.

Magnetic north refers to the direction a compass moves relative to the true north. The small piece of metal in a compass is directly affected by the existence of the electromagnetic force, in this case, the EMF of the earth itself. As to why there is a 1.5 degree offset, no one knows. But the earth does create from its core an EMF.