Halliday, Resnick & Walker — Magnetic Fields: Problem 7

7 Figure 28-23 shows a wood cylinder of mass \( m = 0.150 \text{ kg} \) and length \( L = 0.100 \text{ m} \), with \( N = 13.0 \) turns of wire wrapped around it longitudinally, so that the plane of the wire coil contains the long central axis of the cylinder. The cylinder is released on a plane inclined at an angle \( \theta \) to the horizontal, with the plane of the coil parallel to the incline plane. If there is a vertical uniform magnetic field of magnitude \( 0.92 \text{ T} \), what is the least current \( i \) through the coil that keeps the cylinder from rolling down the plane?