Activities | Science | Physics

The loudspeaker

In the second physics activity of the 2014 Easter holiday edition we learned that when the current is flowing through the solenoid (wrapped around a nail) it is converted into a permanent magnet: chemical energy-> magnetic energy.

This activity is designed to check if the variable electrical signal of the MP3 converts the solenoid into a variable-polarity magnet when it flows through it.  If so, the solenoid would be at times drawn and at other times pulled by another permanent magnet located inside it.  This variation would force the membrane glued to the solenoid to oscillate and produce sound!

Learning about the composition of a loudspeaker: does it contain a magnet?

Learning about the composition of a loudspeaker: does it contain a copper coil?





Learning about the composition of a loudspeaker: does the membrane of the loudspeaker vibrate when it is connected to the MP3?

Material for the construction of a low-quality loudspeaker

• 1 metre of insulated copper wire with a thickness of about 1mm recovered from waste electrical equipment; 
• A very powerful neodymium magnet;
• Adhesive tape;
• Lighter to burn off the wire insulation.

 Where can we get insulated copper wire for six 1-metre coils?

How can we easily make a solenoid for the loudspeaker?

You just have to wrap the copper wire around a thick marker pen 20 times.  The diameter of the pen has to be slightly higher than 12 mm because this is the diameter of our magnet.

 The tape can serve as a membrane for our loudspeaker, surrounding the copper solenoid with the permanent magnet inside.

Does the loudspeaker work when connected to the MP3?

The sound of the loudspeaker is only audible when held against the ear! To improve the loudspeaker a much thinner and longer copper wire, as well as a better membrane, would have to be used.

For further details on these activities carried out on 11 June 2014 (Summer holiday activities) click here.

Activity instructor: Rosa Brígida (UDMF)