Magnetic force on a current-carrying wire (F=NBil)
1. Drag the B-field to the coil, the side(s) lying inside the field will be acted by magnetic force(s).
2. The position and the size of the field region can be varied by dragging its centre or sides.
3. To avoid complexity (induced current), the circuit is broken when the B-field or the number of turns is varied.
4. The net vertical force (downward minus upward) will be shown in the scale reading.
5. When the switch shown is turned to "Zero", the scale reading becomes zero. Afterwards, only the weight added is read. "N" stands for the unit newton; "mN" stands for millinewton.