Act18_sol - Activity 18.1: Information Transfer Using...

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69 Period 18 Activity Sheet Solutions: Information Transfer Activity 18.1: Information Transfer Using Electrical Energy a) Loudspeakers 1) Briefly connect the loudspeaker on your table to a 1.5 volt battery. Place your hand on the speaker as someone quickly connects and disconnects the battery. What do you feel? What happens to the loudspeaker cone as you connect and disconnect the battery? The loudspeaker cone moves as you connect and disconnect the battery. 2) What makes the loudspeaker cone move? A current flows through a coil of wire, which is connected to the cone of the speaker. A permanent magnet in the loudspeaker exerts a force on the current in the coil. The current thus experiences a force, whose strength is proportional to the amount of current. The coil moves in a pattern, which is the same as the pattern of the current in the coil. b) Microphones 3) How is sound transferred by a microphone? Pressure waves from sound cause a coil of wire to move near an electromagnet. The motion of the coil in the magnetic field of the magnet induces a changing current in the coil of wire. Information from the pattern of sounds moving the magnet is turned into a changing electric current. You see the results of these patterns on the oscilloscope screen. 4) How is a microphone similar to loudspeaker? How do they differ? Both microphones and loudspeakers use induced current and magnetic fields to make energy conversions between sound waves and a changing current. They both use coils of wire in a magnetic field and permanent magnets to do so. However, a microphone converts sounds waves into a changing current, while a loudspeaker converts a changing current into sound waves. 1) Your instructor will demonstrate a microphone connected to an oscilloscope. Draw or describe the pattern you see on the oscilloscope screen when the microphone is not in use.
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Act18_sol - Activity 18.1: Information Transfer Using...

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