Forces between a Charge and a Bar Magnet Learning Goal: To understand the forces between a bar magnet and 1. a stationary charge, 2. a moving charge, and 3. a ferromagnetic object. A bar magnet oriented along the y axis can rotate about an axis parallel to the z axis. Its north pole initially points along j. Figure 1 of 3 Interaction of stationary charge and bar magnet A positive charge is placed some distance in the i direction from the magnet. (Figure 1) Assume that no charges are induced on the magnet. Part A Assume that the length of the magnet is much smaller than the separation between it and the charge. As a result of magnetic interaction (i.e., ignore pure Coulomb forces) between the charge and the bar magnet, the magnet will experience which of the following? A torque due to the charge attracting the north pole of the manget A torque due to the charge attracting the south pole of the magnet A torque only if one magnetic pole is slightly closer to the charge than the other No torque at all Submit My Answers Give Up Interaction of moving charge and bar magnet Consider a second case in which the charge is again some distance in the direction from the magnet, but now it is moving toward the center of the bar magnet, that is, with its velocity along i. (Figure 2) Part B Due to its motion in the magnetic field of the bar magnet, the charge will experience a force in which direction? Hints - - +k -k Submit My Answers Give Up Interaction of iron and har magnet Figure 2 of 3 Figure 3 Iron Nail of 3 magnet Now the charge is replaced by an electrically neutral piece of initially unmagnetized soft iron (for example, a nail) that is not moving. (Figure 3) Part C As a result of the magnetic interaction between the soft iron and the bar magnet, which of the following will occur? Hints The magnet will experience a torque due to the iron attracting its north pole. The magnet will experience a torque due to the iron attracting its south pole. Whichever pole of the magnet is closest to the iron will be attracted to the iron. Whichever pole of the magnet is closest to the iron will be repelled from the iron. Submit My Answers Give Up