b)Loudspeakers operate using permanent magnets. In order to translate an electrical signal into an audible sound, speakers contain an electromagnet. An electromagnet is a metal coil which creates a magnetic field when an electric current flows through it. This coil behaves much like a normal permanent magnet, with one particularly asset – it can reverse the direction of the current in the coil to flip the poles of the magnet.Inside a speaker, an electromagnet is placed in front of a permanent magnet. The permanent magnet is fixed firmly into position whereas the electromagnet is mobile. As pulses of electricity pass through the coil of the electromagnet the direction of its magnetic field is rapidly changed. This means that it is in turn attracted to and repelled from the permanent magnet, vibrating back and forth.The electromagnet is attached to a cone made of a flexible material such as paper or plastic which amplifies these vibrations, pumping sound waves into the surrounding air and
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