This section covers the properties of magnets, magnetization, the relationship between magnets and electric current, and the force exerted on magnets and current-carrying wires in magnetic fields. Key concepts include: - Magnetic field lines point outward from the north pole of a magnet and inward towards the south pole, and unlike poles attract while like poles repel. - Earth can be thought of as containing a giant magnet, with the north magnetic pole near the geographic South Pole and the south magnetic pole near the geographic North Pole. - Cutting a bar magnet in half will result in two smaller magnets, each with a north and a south pole. - Ferromagnetic materials can become magnetized, forming domains that act like small bar magnets. This process can be made permanent by heating and cooling or by tapping the material in the presence of other magnets. - A magnetic field can be mapped out using a small compass or iron filings, and the direction of the magnetic field lines can be determined using the right-hand rule. - Moving charges produce a magnetic field, and the reverse is also true: a charge moving through a magnetic field will experience a force. The magnitude of this force depends on the charge, velocity, and magnetic field, and the direction follows the right-hand rule. - A current-carrying wire in a magnetic field experiences a force, with the direction determined by the right-hand rule as before. The magnitude of the force on a straight wire of length L in a magnetic field B, moving with velocity v, is given by F = ILB sin(θ), where θ is the angle between the magnetic field and the current. Key terms introduced: - Magnetic poles: The parts of a magnet that exert the strongest force on other magnets or magnetic materials. - Magnetization: The process of magnetizing aferromagnetic material, either by an external magnet or by heating. - Magnetic dipole: A magnet that has two opposite poles. - Domains: Small regions within a magnetic material that act like small bar magnets. - Permeability of free space: A constant (µ0 = 4π x 10^-7 T•m/A²) that appears in magnetic fields created by current-carrying wires. - Electromagnet: A device that creates a magnetic field using electric current. - Magnetohydrodynamic drive: A proposed propulsion system that uses the force on charged particles moving in a magnetic field. - Magnetohydrodynamics: The study of the motion of electrically charged fluid, such as plasma, in a magnetic field. Video: Introduction to Magnetism, Using a Compass to Map Out the Magnetic Field, and Magnetic Field Due to an Electric Current - Quiz questions: 1. Toward which magnetic pole of Earth is the north pole of a compass needle attracted? A. North magnetic pole of Earth, which is located near the geographic North Pole of Earth B. South magnetic pole of Earth, which is located near the geographic North Pole of Earth C. North magnetic pole of Earth, which is located near the geographic South Pole of Earth D. South magnetic pole of Earth, which is located near the geographic South Pole of Earth 2. With the slider at the top right of the simulation window, set the magnetic field strength to 100 percent . Now use the magnetic field meter to answer the following question: Near the magnet, where is the magnetic field strongest and where is it weakest? Don't forget to check inside the bar magnet. A. The magnetic field is strongest at the center and weakest between the two poles just outside the bar magnet. The magnetic field lines are densest at the center and least dense between the two poles just outside the bar magnet. B. The magnetic field is strongest at the center and weakest between the two poles just outside the bar magnet. The magnetic field lines are least dense at the center and densest between the two poles just outside the bar magnet. C. The magnetic field is weakest at the center and strongest between the two poles just outside the bar magnet. The magnetic field lines are densest at the center and least dense between the two poles just outside the bar magnet. D. The magnetic field is weakest at the center and strongest between the two poles just outside the bar magnet and the magnetic field lines are least dense at the center and densest between the two poles just outside the bar magnet. Answers: 1. A 2. A

Last modified: Wednesday, 22 January 2025, 3:21 PM