When the coil carries a current, it experiences a force. State what else is required in a loudspeaker for a current-carrying wire to experience a force.
A student connects the coil to the output of an alternating current (a.c.) generator. Fig. 8.2 shows how the electromotive force (e.m.f.) from the generator varies with time. Explain why the e.m.f. shown in Fig. 8.2 causes the coil to vibrate.
The vibrating cone generates sound in the air around it. Explain, in terms of molecules, how the cone creates a sound wave that travels through the air.
Sound is a longitudinal wave. Describe how a longitudinal wave differs from a transverse wave.
Using Fig. 8.2, find how many times the cone changes direction of motion in $1.0\,\text{s}$.
The speed of sound in air is $340\,\text{m s}^{-1}$. Calculate the wavelength of the sound.
The student changes the generator so that the maximum output voltage is now $3.0\,\text{V}$. All other details remain the same as in the output shown on the graph in Fig. 8.2. Explain any effect on the loudness of the sound.
Explain whether there is any effect on the pitch of the sound.