Getting to Know Electricity to Motion and Sound Energy

You might have experienced the vibrations coming from a speaker when the music is turned up to a high volume This occurs because music like all sound energy is made up of waves Sound waves are vibrations that move through a medium like air water wood or even your body

Some devices like speakers use electricity to produce sound Using electricity in this way givesus

control over the amount of energy carried by

sound waves When we turn up the volume of a stereo we are adding energy to the sound waves produced by the speaker You can feel the vibrations of sound

energy coming from the speakers at a loud concert A speaker is just one device that uses electrical

energy to produce sound energy Can you think of other examples CD players and telephones also transform electrical energy to sound energy They do this using the process of electromagnetic induction

What is electromagnetic induction Despite its long name electromagnetic induction basically comes down to a simple principle If you move a permanent magnet near a coil or wire or move a wire through a magnetic field an electric current is produced This is the basic relationship behind most of the ways we produce electricity Energy sources such as wind moving water or burning coal are often used to generate electricity In a wind turbine for example the mechanical energy of moving wind causes the turbine to spin This spins a coil in a magnetic field and electricity is produced When coal is burned in a power plant water is often heated to produce steam The rising steam turns a turbine in a magnetic field to produce electricity

Misconception 1 If you attach a string to two cups and pull them so the string is tight you can use the cups like a telephone Thatrsquos how the first telephones worked right

Thatrsquos not exactly how they worked Although wires connected the first telephones sound energy did not travel along the wires Instead the sound energy of a voice at one end of the phone was changed into electrical energy This was then transmitted by electric current to the phone receiver at the other end There the electrical energy was converted back to sound waves that the listener could hear

Concept Electricity to Motion and Sound Energy Getting to Know wwwdiscoveryeducationcom

1 copy Discovery Education All rights reserved

Discovery Education is a subsidiary of Discovery Communications LLC

How do speakers and microphones change electrical energy into sound

A speaker uses electromagnetic induction too The speaker contains both an electromagnet and a permanent magnet To produce a sound an electrical current causes the electromagnet to move rapidly This interaction between the two magnets causes vibrations The vibrations are transmitted to a flexible cone This flexible cone generates sound waves as it moves back and forth in response to pulses of electrical current Speakers change electrical energy into sound

A wind farm uses wind turbines to produce electrical energy

Similar to speakers microphones use the same principles to change sound into electrical energy only in reverse Sound waves enter a microphone and cause parts inside to vibrate Inside there is a coil of wire surrounded by a permanent magnet The vibrations induce an electric current in the coil Thus the vibrations caused by the sound waves are changed into electrical current This current then travels to a speaker which changes it back into sound waves so you can hear them

Electrical power plants speakers and microphone all rely on electromagnetic induction

Misconception 2 I heard that magnets are used to produce electricity That canrsquot be right The magnets on the outside of my refrigerator arenrsquot electrical

Not all magnets are electrical However magnetism and electricity are related to one another Thatrsquos why we use the term ldquoelectromagnetismrdquo Electric current can be used to make a powerful magnet called an electromagnet Electromagnets can be turned on and off by closing and opening a circuit You can also use magnets to produce electric current

Concept Electricity to Motion and Sound Energy Getting to Know wwwdiscoveryeducationcom

2 copy Discovery Education All rights reserved

Discovery Education is a subsidiary of Discovery Communications LLC