This reversing-current-reverses-force lesson keeps the same magnetic-force magnitude but flips the force direction when the current arrow reverses. The 24 N magnitude is exact only for the stated 2 T, 3 A, 4 m perpendicular-wire row and finite direction table. Real demonstrations depend on alignment, field uniformity, wire heating, contact resistance, support friction, calibration, finite precision, and measurement uncertainty.
The finite direction table flips when the current arrow reverses. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Reversing current keeps the force magnitude
The same field 2, current 3, and length 4 still give 24 newtons.
2×3×4=24
Only the finite force direction flips
The reversed current changes the direction table result from up to down, not the value 24.