Couple sur un cadre rectangulaire parcouru par un courant
This 3D simulation isolates the forces acting on each side of a rectangular current-carrying coil placed in a uniform magnetic field, and shows how they combine into a turning effect. Rotating the coil while watching the force arrows explains where the cosine in the torque formula comes from.
Comment utiliser cette simulation
- Rotate the coil to any orientation in the field
- Change the current, field strength and number of turns
- Toggle the force vectors on and off
Ce qu’il faut observer
- Torque is maximum when the coil plane is parallel to the field
- Torque falls to zero when the coil plane is perpendicular to the field, even though the forces are still there
- Forces on the sides parallel to the field cancel and never contribute
La physique derrière
The two sides perpendicular to the field carry current in opposite directions and feel forces F = BIL in opposite directions, forming a couple. The torque is τ = BIAN·cosθ, where θ is the angle between the coil plane and the field. The other two sides produce forces that act along the same line and simply cancel, contributing no torque.