Bell's transducer (which was both microphone and earpiece) depended on electromagnetic induction - the principle of the interconvertibility of magnetism and electricity - which had been demonstrated by Michael Faraday in the 1830s: if a magnet is moved through the centre of a coil of wire, an electric current is 'induced' in the wire which is proportional to the magnet's motion.
(Bell's transducer; was; both microphone and earpiece) (the wire; is; proportional to the magnet's motion) (Bell's transducer; depended; on electromagnetic induction) (the interconvertibility of magnetism and electricity; had been demonstrated; by Michael Faraday; L:in the 1830s) (a magnet; is moved; through the centre of a coil of wire) (an electric current; is induced; L:in the wire)
Bell's transducer the wire Bell's transducer the interconvertibility of magnetism and electricity a magnet an electric current
was is depended had been demonstrated is moved is induced
both microphone and earpiece
proportional to the magnet's motion
on electromagnetic induction
by Michael Faraday L:in the 1830s
through the centre of a coil of wire
L:in the wire