These three schematics show a very simplified and impractical electric motor, its rotor having just one coil and no core. The coil has a length a = 0.0289 m and total width b=0.0231 m. It can rotate about an axis that is out of the page for Figure 3 and approximately out of the page for Figure 1. For the calculation, we shall pretend that the field is uniform with magnitude 2.1 T upwards, as shown. Because of the split ring, the current, i = 17.8 A, always travels out of the page in the upper edge of the coil and into the page in the lower edge. The normal to the plane of the coil makes an angle 79° to the magnetic field B, as shown in Figure 2. N S N trub aplit ring Figure 1. A rectangular coil of wire lies between two permanent magnets. A current i runs through the wire. b Figure 2. The coil has side length a and b. B Figure 3. Cross section of the rectangular coil in the magnetic field. The normal of the coil lies at an angle to the magnetic field. SN SN

These three schematics show a very simplified and impractical electric motor, its rotor having just one coil and no core. The coil has a length a = 0.0289 m and total width b=0.0231 m. It can rotate about an axis that is out of the page for Figure 3 and approximately out of the page for Figure 1. For the calculation, we shall pretend that the field is uniform with magnitude 2.1 T upwards, as shown. Because of the split ring, the current, i = 17.8 A, always travels out of the page in the upper edge of the coil and into the page in the lower edge. The normal to the plane of the coil makes an angle 79° to the magnetic field B, as shown in Figure 2. N S N trub aplit ring Figure 1. A rectangular coil of wire lies between two permanent magnets. A current i runs through the wire. b Figure 2. The coil has side length a and b. B Figure 3. Cross section of the rectangular coil in the magnetic field. The normal of the coil lies at an angle to the magnetic field. SN SN