Magnetic wire force changes with field and finite direction. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
One tesla gives eight newtons
Field 1 T, current 2 A, and length 4 m give force 8 N with direction up.
F=1×2×4=8
Doubling field doubles the force
Field 2 T, current 2 A, and length 4 m give force 16 N with direction up.
F=2×2×4=16
Reversing current flips direction, not size
Field 2 T, current 2 A, and length 4 m give force 16 N with direction down.