An engineer is testing a prototype electromagnetic propulsion track. A straight rigid conductor of length l l\,l is suspended horizontally between the poles of a strong permanent C-shaped magnet as shown in the diagram below. The conductor is connected in series with a DC power supply and an open switch.
Explain what happens to the conductor immediately after the switch is closed, describing the magnetic interactions involved.
The section of the conductor situated at right angles to the uniform magnetic field has a length of 0.45 m. The permanent magnet has a magnetic flux density of 0.15 T0.15\text{ T}0.15 T.
When the switch is closed, the conductor experiences an electromagnetic force of 0.189 N. Calculate the current flowing through the circuit. Use the equation:
F=BIlF = B I lF=BIl