Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Name Lesson 2 Summary Use with pp. 482–489 Lesson 2: How are electricity and magnetism related? Vocabulary electric current a flow of electric charge in a material electric circuit a closed path along which current can flow magnetic domain a large number of atoms with their magnetic fields pointing in the same direction electric motor a device that changes electrical energy to kinetic energy generator a device that changes mechanical energy into electrical energy In some materials, electrons move from atom to atom causing an electric charge to move along the atoms. Electrons have negative charges. This causes them to push away from each other. Electrons are pushed from atom to atom to produce an electric current. Electric Circuit A series circuit is an electric circuit with only one path for a current to flow through. Look at the circuits on page 483 in your textbook. The current flows from the negative side of the battery, through each light bulb, and back to the positive side of the battery. If you take out a bulb, this causes the other bulb to go out too. Parallel circuits have an advantage over series circuits. They have more than one path for the current to flow through. The second bulb will still glow after the first bulb goes out. Magnetic Fields A magnetic field is the space around a magnet in which it can affect other magnets. A magnetic domain is made up of a large number of atoms whose magnetic fields are pointing in the same direction. If you break a magnet, you will have two smaller magnets whose magnetic domains point in the same direction as the 106 Chapter 17, Lesson 2 Summary original magnet. Each magnet still has a north and a south pole. Earth acts like a giant magnet. It has a magnetic field. This is what causes all compasses to point north. Electromagnets An electromagnet is made of wires wrapped around a magnet. Electric current is sent through the wires creating a magnetic field. An iron core placed into the coil of wires will make it stronger. The current in the wire magnetizes the iron. Electromagnets only attract magnetic objects when the current is turned on. An electric motor is made of an electromagnet, a permanent magnet, and an object that changes the direction of the electric current. An electric motor changes electrical energy to kinetic energy. Magnetism and Electricity Magnetic fields can also be used to make electric current in a wire. First, a magnet must be moved through a wire coil. The wire experiences a changing magnetic field that produces a current in the wire. A generator changes mechanical energy into electrical energy. Generators are made of a permanent magnet and a coil of wire. A source of mechanical energy causes the coil to spin in the field of the magnet. The coil must spin in order to produce an electric current. Quick Study © Pearson Education, Inc. 6 Electric Current Name Lesson 2 Checkpoint Use with pp. 482–489 Lesson 2 Checkpoint 1. What advantage do parallel circuits have over series circuits? 2. Sequence Look at the series circuit on page 483 of your textbook. Describe the movement of current as it leaves the negative side of the battery until it reaches the positive side. 3. Why can’t a magnet have just a north pole? 4. Explain how electricity and magnetism work together in a motor. 5. Sequence Make a numbered list, in your own words, of steps in which an electric motor changes electrical energy to kinetic energy. See page 487 of your textbook for some help. © Pearson Education, Inc. 6 6. Describe how electricity flows through a series circuit and a parallel circuit, or draw diagrams on a separate sheet of paper. 7. Why does the coil have to spin in a generator? Quick Study Chapter 17, Lesson 2 Checkpoint 107