Loudspeakers (physics only) (HT only) — AQA GCSE Physics
Test yourself on Loudspeakers (physics only) (HT only) with AQA GCSE practice questions.
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Loudspeakers (physics only) (HT only) explained
Questions on this show a cross-section: a cylindrical magnet with the coil sitting in the narrow gap between its north and south poles, the coil fixed to the narrow end of a paper cone, and the cone held at its rim by a flexible surround.
Read the full explanation
Reading that diagram is half the answer. The field in the gap runs across the coil, so the force on the coil acts along the axis of the cone, in or out, and the flexible surround lets the coil and cone move freely and spring back. Headphones are the same device made small: a light coil and a thin diaphragm instead of a large cone, driven by a much smaller current, which is why they can be run straight from a phone. In both, the frequency of the sound matches the frequency of the current, and the amplitude of the movement sets the loudness.
Your focus
- Identify the coil, magnet, cone and surround on a cross-section of a moving-coil loudspeaker.
- Explain why the coil moves along the axis of the cone instead of rotating.
- Compare a pair of headphones with a loudspeaker, naming what is the same and what is scaled down.
Show all 4 objectives
- Predict what a listener hears if the current in the coil is made steady rather than alternating.
Loudspeakers (physics only) (HT only) exam tips
Marking Points
- one mark for identifying the coil sitting in the gap between the poles of the permanent magnet
- one mark for the force on the coil acting along the axis, in or out, so the coil moves rather than turns
- one mark for the cone or diaphragm being attached to the coil and moving with it
- one mark for linking the frequency of the current to the frequency of the sound produced
- one mark for linking the size of the current to the amplitude of the vibration and so to the loudness
Examiner Tips
- 💡Label the coil, magnet, cone and surround on the given figure, then use those labels in your sentences.
- 💡Mention one thing that changes the loudness and one that changes the pitch; questions often ask for both.
- 💡A steady direct current holds the cone in one position and makes no sound; say so if you are asked.
Common Mistakes
- labelling the cone as the part that carries the current, when it is the coil
- saying the coil rotates like a motor coil, when the arrangement of the field makes it move in and out
- treating headphones as a different mechanism rather than a small moving-coil loudspeaker
- leaving the permanent magnet out of the explanation, so there is no field for the current to interact with