Starter quiz
- The abbreviation ‘p.d.’ stands for an electrical quantity. What is the full name of this quantity and what is its unit?
- positive difference, measured in amps
- potential difference, measured in amps
- positive difference, measured in volts
- potential difference, measured in volts ✓
-
- Each of the diagrams shows a wave, with distance along the horizontal axis. All of the diagrams have the same scale. Which two of these waves have the same amplitude?
- An object makes a sound. Which of the following must the object be doing?
- rotating
- vibrating ✓
- changing state
- changing its temperature
- moving from one place to another
-
- Which of the following are correct definitions of the frequency of a wave?
- the distance between the wave’s centre line and a peak
- the distance between the wave’s centre line and a trough
- the number of wavelengths created per second ✓
- the time taken for one wavelength to be created
- the number of wavelengths that pass a point each second ✓
-
- Which of the following statements are correct?
- The pitch of a sound is how low or high it is. ✓
- The pitch of a sound is how loud or quiet it is.
- The amplitude of a sound wave sets the pitch of the sound.
- The frequency of a sound wave sets the pitch of the sound. ✓
-
- When a loudspeaker makes a sound, a part of it called the cone moves backwards and forwards. How does the motion of the cone change if the loudspeaker now makes a louder sound with the same pitch?
- The cone moves faster. ✓
- The cone moves a greater distance backwards and forwards. ✓
- The cone moves backwards and forwards more times per second.
- The cone takes less time to move backwards and forwards once.
-
Exit quiz
- Match each of the following devices to a description of what it does.
- oscilloscope⇔displays a representation of a sound wave ✓
- loudspeaker⇔produces sound from an electronic signal ✓
- microphone⇔produces an electronic signal from sound ✓
- Each of the diagrams shows an oscilloscope trace of a sound wave. All of the diagrams have the same scale. Which of the sound waves have the same pitch?
The diagram shows the coil, cone and permanent magnet of a loudspeaker. The coil is connected to an AC power supply. Which of the following statements are correct?- When there is a current in the coil, it becomes an electromagnet. ✓
- When current flows in the coil, the coil is attracted to the permanent magnet.
- The lower the frequency of the alternating voltage, the louder the sound.
- The lower the p.d. across the coil, the quieter the sound. ✓
-
- Sort the following statements into the correct order to describe the operation of a moving–coil microphone.
- 1⇔A sound wave hits the diaphragm (cone).
- 2⇔This makes the diaphragm (cone) vibrate.
- 3⇔This causes an alternating p.d. to be induced across the coil.
- 4⇔This causes a current in the circuit attached to the coil.
- 5⇔The pattern of varying current matches the pattern of varying sound.
- In which of the following ways does an amplifier change an electronic signal?
- It increases the signal’s p.d. without changing its frequency. ✓
- It increases the signal’s frequency without changing its p.d.
- It increases the signal’s p.d. and increases its frequency.
- It increases the signal’s p.d. and decreases its frequency.
-
- Which of the following statements are correct?
- A loudspeaker uses the motor effect. ✓
- A microphone uses the motor effect.
- A loudspeaker uses the generator effect.
- A microphone uses the generator effect. ✓
-
Worksheet
Loading worksheet ...
Presentation
Loading presentation ...
Video
Lesson Details
Key learning points
- A sound can be represented by an electronic signal changing in time to match the sound wave.
- Loudspeakers use the motor effect to convert electrical signals into sound waves.
- A moving–coil loudspeaker is made from a cone connected to a coil of wire that moves in relation to a fixed magnet.
- Microphones use the generator effect to convert sound waves into electrical signals.
- A moving–coil microphone is made from a diaphragm connected to a coil of wire that moves in relation to a fixed magnet.
Common misconception
It is common for pupils to hold the misunderstanding that stationary magnetic fields can attract or repel electric charge or to conflate magnetic and electrostatic effects.
Provide opportunities for pupils to explain applications of the motor effect and the generator effect in order to consolidate a scientific understanding.
Keywords
Oscilloscope - A piece of equipment that can display a representation of a sound wave.
Motor effect - The effect of causing movement between a magnet and an electromagnet.
Moving-coil loudspeaker - A loudspeaker that produces sound using the motor effect.
Generator effect - The effect of inducing a current by the relative movement of a circuit and a magnetic field.
Moving-coil microphone - A microphone that produces an electric signal from sound using the generator effect.
+