Transcript File
Think about it . . In the space provided on page 95 answer these questions; 1. Can you change the direction of a compass without using a bar magnet and how? 1. Can you change the strength of an electromagnet? Magnetism from electricity CHAPTER 16, SECTION 2 State Standard: 12.1- Recognize that electricity can be produced using a magnet and wire coil The Discovery of Electromagnetism ● Danish physicist Hans Christian Oersted (UHR STED) discovered the relationship between electricity and magnetism in 1820. ● During a lecture, he held a compass near a wire carrying an electric current. Oersted noticed that when the compass was close to the wire, the compass needle no longer pointed to the north. ● The French scientist André-Marie Ampère did more research with electricity and magnetism. Oersted’s Experiment Solenoids ● A solenoid is a coil of wire that produces a magnetic field when carrying an electric current. ● In fact, the magnetic field around a solenoid is very similar to the magnetic field of a bar magnet. ● The strength of the magnetic field of a solenoid increases as more loops per meter are used. ● The magnetic field also becomes stronger as the current in the wire is increased. Electromagnets ● An electromagnet is made up of a solenoid wrapped around an iron core. ● The magnetic field of the solenoid makes the domains inside the iron core line up. ● The magnetic field of the electromagnet is the field of the solenoid plus the field of the magnetized core. As a result, the magnetic field of an electromagnet may be hundreds of times stronger than the magnetic field of just the solenoid. Go to page 435 in your textbook ● Read this page and provide the appropriate responses in your manual. ● Be prepared to share your answers. ● Can a magnet cause a current-carrying wire to move? Explain: YES. The electric current creates a magnetic field that exerts a force on the wire and causes the wire to change directions when the current flow changes directions. Electric Motors DEMO ● An electric motor is a device that changes electrical energy into mechanical energy. ● All electric motors have an armature—a loop or coil of wire that can rotate. ● The armature is mounted between the poles of a permanent magnet or electromagnet. ● A commutator is split half rings attached to the ends of the armature to reverse the current direction. ● Current enters the armature through brushes that touch the commutator. ● Every time the armature and the commutator make a half turn, the direction of the current in the armature is reversed. A Direct-Current Electric Motor Put it together. . . In the space in your notes answer the following; 1 – Explain how you can vary the strength of an electromagnet 1) Increase electric current. 2) Increase the coils on a solenoid 2 – Go to page 437 in your textbook and answer number 8. NO. The loops must be wire not magnets. The core must have iron in it. Be prepared to share your answers. Putting it Together… ●Complete the skill sheet ●It is homework due tomorrow if it is not finished in class.