magnetism - loudspeakers and headphones

Question 1

how is motor effect used in a loudspeaker/headphones?

Answer 1

• in a loudspeaker there is a cone with a coil of wire wrapped around one end. coil of wire connected to an alternating current (AC) electrical supply. also have a permanent magnet which goes inside the coil of wire
• as current passes through the coil, it generates a magnetic field
• magnetic field from coil now interacts with magnetic field from permanent magnet.
• these magnetic fields attract or repel each other causing a resultant force which causes the cone to move
• when current switches direction, direction of force on the cone reverses. causes cone to move in and out generating sound waves
• by changing frequency of AC supply, changes frequency that the cone vibrates
• if we increase size of current, we increase amplitude of the vibration. increasing volume of sound

Question 2

High frequency of alternating current =
Low frequency=

Answer 2

higher pitch sound
lower pitch sound