A packaging machine uses the motor effect to move a current-carrying conducting bar. The part of the bar inside the uniform magnetic field is at right angles to the field. The machine is tested using two settings.
| Setting | Magnetic flux density in T | Current in A | Length of bar inside the field in mm |
|---|---|---|---|
| P | 0.24 | 3.0 | 40 |
| Q | 0.18 | unknown | 80 |
The force on the bar must be the same in both settings.
Calculate the current needed in setting Q.