# can someone help me with gcse physics

I do Edexcel iGCSE and we have to do loudspeakers and stuff
is this a correct answer for how a loudspeaker works?
ac flows through coil and makes it an electromagnet

the ac causes the magnetic field of the electromagnet to continuously change

this means it is constantly being repelled and attracted by the permanent magnet

the constant change in direction of the force acting on the coil causes it to move back and forth

this causes the cone to vibrate and sound waves to be produced
Hi,
I think this is quite a logical, correct and flowing set of steps to describe the functioning of a loudspeaker. My suggestion would be to strengthen your understanding by learning about the mechanisms of other applications of electromagnetism e.g. electric bell and electric motor.

Well done!
(edited 1 month ago)
Original post by macpatgh-Sheldon
Hi,
I think this is quite a logical, correct and flowing set of steps to describe the functioning of a loudspeaker. My suggestion would be to strengthen your understanding by learning about the mechanisms of other applications of electromagnetism e.g. electric bell and electric motor.
Well done!

thank you! I understand electric motor and dynamo too I just don't get ac generator
Original post by saffronarora
thank you! I understand electric motor and dynamo too I just don't get ac generator

Ok let me try to help u [if my photographic memory does not let me down after 15+ years - sorry if that implies a wide temporal width lol 😄].

First just recall i.e. bring to the forefront of your mind an electric motor - you will know it has a commutator to reverse the direction of the magnetic field every half-turn yeah [otherwise oc the rotor/blade will turn half a turn and just stop there end of story, agreed?

Ok with an AC generator, think of the reverse of the above i.e. as you say a dynamo [which you have grasped e.g. the type that was used to provide electrical power to a bicycle light years ago that used a dynamo fitted in contact with the rear tyre rim and as the cyclist pedalled it generated electricity [ask grandad]] - because this dynamo had a commutator, it provided DC power.

Now, with an AC generator, THERE IS NO COMMUTATOR, so that as the water [e.g. as in Kenya where my village had a hydroelectric power station at the bottom of a waterfall and the force of the water due to gravity [in common with Owen falls with the Nile in Jinja, Uganda]] rotates the turbines they generate power, BUT THE DIFFERENCE IS THAT WITH EACH HALF-ROTATION OF THE TURBINE, the direction of the electromagnetic flux generated changes by 180o , so the direction of the current generated ALSO CHANGES WITH EACH TURN i.e. it generates Alternating Current [AC]. [important diference to remember from the dynamo is that AC generator has NO COMMUTATOR. It is worth knowing that standard AC power e.g. from a socket on the wall, provides current that changes direction 50 times a second [in general i.e. its frequency is 50 Hz].

HELP ANY PHYSICS GRADUATES ON TSR: If I am talking nonsense i.e. if my memory is failing me (😟), please explain the reality @Reality Check ??! Ta!

M [specialist biology tutor, medical author, trainer in medical software, clinical pharmacologist, etc]
(edited 1 month ago)
Original post by saffronarora
I do Edexcel iGCSE and we have to do loudspeakers and stuff
is this a correct answer for how a loudspeaker works?
ac flows through coil and makes it an electromagnet
the ac causes the magnetic field of the electromagnet to continuously change
this means it is constantly being repelled and attracted by the permanent magnet
the constant change in direction of the force acting on the coil causes it to move back and forth
this causes the cone to vibrate and sound waves to be produced

Alternating current supplied to the loudspeaker creates sound waves in the following way:

1.

a current in the coil creates a magnetic field

2.

the magnetic field interacts with the permanent magnet generating a force, which pushes the cone outwards

3.

the current is made to flow in the opposite direction

4.

the direction of the magnetic field reverses

5.

the force on the cone now pulls it back in

6.

repeatedly alternating the current direction makes the cone vibrate in and out

7.

the cone vibrations cause pressure variations in the air - which are sound waves

thank you everyone !