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Name ______________________________ Lesson 3 Summary Use with pp. 54–59 Lesson 3: How are electric currents and magnetic fields related? Vocabulary electromagnet a coil of wire through which electric current passes, creating a magnetic field In 1820, a scientist named Hans Christian Oersted ran electric current through a wire. There was a compass near the wire. When Oersted turned on the current, the compass needle moved. The electric charges created a magnetic field. Moving Magnets Produce Electricity In 1831, the scientist Michael Faraday put a moving magnet inside a wire coil. This created an electric current. Faraday invented a device called a dynamo. A dynamo has a magnet inside a coil of wire. When the magnet moves back and forth, the dynamo produces electricity. When the magnet stops moving, the electric current stops. This shows that electric current and magnetic fields are related. Electric charges in motion create magnetism. Electric charges in motion also create electric current. Electromagnets An electromagnet is made of a coil of wire. Electric current moves through this coil of wire. The moving electric current creates a magnetic field. Here are some ways to make an electromagnet stronger. You can put an iron or steel bar inside the coil of wire. A thicker bar makes a stronger electromagnet. Or, you can add more coils or more 12 Chapter 2, Lesson 3 Summary layers of wire. You can also wrap the coils more tightly around the bar. A stronger current also makes an electromagnet stronger. Applications of Electromagnets People use electromagnets in many ways. Computers use electromagnets. A computer’s hard drive is covered with magnetic material. When you save a file, the computer uses electromagnetic fields. The electromagnets “write” the information. Doctors use electromagnets to see tissues deep inside the body. MRI stands for Magnetic Resonance Imaging. An MRI machine produces a magnetic field. This field affects particles in the body. A computer uses these particles to take a picture of the body. Some flashlights use an electromagnet to make light. When you shake the flashlight, a magnet moves through a coil of wire. This produces the electric current. The electric current produces light. In junkyards, large cranes have strong electromagnets in them. The cranes use the magnets to lift large, heavy pieces of metal. Intervention Study Guide © Pearson Education, Inc. 4 Electric Current Produces a Magnetic Field Name ______________________________ Lesson 3 Questions Use with pp. 54–59 Lesson 3 Questions 1. How does a dynamo produce electricity? 2. What are two ways to make an electromagnet stronger? © Pearson Education, Inc. 4 3. What is one device that people use every day in school and at work that uses electromagnets? Intervention Study Guide Chapter 2, Lesson 3 Questions 13