A piece of equipment that can display a representation of a sound wave.

The effect of causing movement between a magnet and an electromagnet.

A loudspeaker that produces sound using the motor effect.

The effect of inducing a current by the relative movement of a circuit and a magnetic field.

A microphone that produces an electric signal from sound using the generator effect.

Applications of motor and generator effects

Physics

In the Magnets and electromagnets unit, pupils learnt about rules for magnets, magnetic fields of bar magnets, and the properties and uses of electromagnets. 

This unit explores magnetism, including permanent and induced magnets, magnetic fields, and Earth's magnetism. It covers current-induced magnetic effects, electric motors, and devices like microphones and loudspeakers, with an emphasis on models, calculations, and practical applications.

Electromagnetism

displays a representation of a sound wave

Match each of the following devices to a description of what it does.

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?

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.

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?

This causes an alternating p.d. to be induced across the coil.

This causes a current in the circuit attached to the coil.

The pattern of varying current matches the pattern of varying sound.

Sort the following statements into the correct order to describe the operation of a moving–coil microphone.

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.

In which of the following ways does an amplifier change an electronic signal?

Which of the following statements are correct?

The abbreviation ‘p.d.’ stands for an electrical quantity. What is the full name of this quantity and what is its unit?

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?

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 are correct definitions of the frequency of a wave?

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.

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.

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?

Introduction

What will you need for this lesson?

Are you ready to learn?

Equipment

Worksheet