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Loudspeakers and microphones: GCSE Combined Science Physics practice questions

Higher tier content · Grade 7

A second set of questions on loudspeakers and microphones. They are different from the ones on the topic page. Try each, then open the answer and compare your working.

More questions

Question 1 Hard

A loudspeaker is driven at 500 Hz. How many times does the cone move back and forth in 2 seconds?

Show answer

Answer: 1000 times

  1. 500 vibrations each second.
  2. 500 × 2 = 1000.

Question 2 Hard

Explain why the cone moves the opposite way when the current reverses.

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Answer: the force on the coil reverses

  1. The force depends on the direction of the current.
  2. So reversing the current reverses the force.

Question 3 Hard

Explain why a microphone needs a magnet and a coil.

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Answer: the moving coil in the magnetic field has a potential difference induced

  1. The coil moves in the magnetic field.
  2. This induces a potential difference.

Question 4 Hard

A 440 Hz signal is made larger in size but not in frequency. State what happens to the sound.

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Answer: it gets louder and the pitch stays the same

  1. The larger current gives a larger amplitude.
  2. The frequency does not change, so the pitch stays the same.

Quick checks

Short questions with options. Choose one before you open the answer.

Check 1

What are the three main parts of a loudspeaker?

  1. a battery, a bulb and a switch
  2. a magnet, a coil and a cone
  3. a magnet, a motor and a fan
Show answer

a magnet, a coil and a cone A permanent magnet, a coil of wire that can move, and a paper cone fixed to the coil.

Check 2

Which part of a loudspeaker pushes on the air?

  1. the cone
  2. the magnet
  3. the wire to the amplifier
Show answer

the cone The paper cone, which is fixed to the coil.

Check 3

What kind of current is used in a loudspeaker?

  1. a direct current
  2. no current is used
  3. an alternating current
Show answer

an alternating current An alternating current, which keeps changing direction.

Check 4

What is a direct current?

  1. a current that keeps changing direction
  2. a current that flows in one direction only
  3. a current that flows in a straight wire
Show answer

a current that flows in one direction only A current that flows in one direction only.

Check 5

Which effect makes the coil in a loudspeaker move?

  1. the motor effect
  2. the generator effect
  3. the greenhouse effect
Show answer

the motor effect The motor effect, which is a force on a current in a magnetic field.

Check 6

What is the motor effect?

  1. a current made by a moving magnet
  2. a magnet that spins by itself
  3. a force on a wire carrying a current in a magnetic field
Show answer

a force on a wire carrying a current in a magnetic field A wire carrying a current in a magnetic field feels a force.

Check 7

What happens to the force on the coil when the current reverses?

  1. it stays the same
  2. it reverses
  3. it becomes zero
Show answer

it reverses The force reverses too.

Check 8

Why does the coil move backwards and forwards?

  1. the current keeps reversing, so the force keeps reversing
  2. the magnet keeps spinning
  3. gravity pulls it up and down
Show answer

the current keeps reversing, so the force keeps reversing The alternating current keeps reversing, so the force keeps reversing.

Check 9

What does the cone do to the air?

  1. heats the air
  2. stops the air moving
  3. makes the air vibrate
Show answer

makes the air vibrate It makes the air vibrate, which sends out a sound wave.

Check 10

How does the frequency of the sound compare with the frequency of the current?

  1. the sound frequency is double
  2. they are the same
  3. the sound frequency is half
Show answer

they are the same They are the same.

Check 11

What does a higher frequency current give?

  1. a higher pitch
  2. a louder sound
  3. a quieter sound
Show answer

a higher pitch A higher pitched sound.

Check 12

What does a larger current give?

  1. a higher pitch
  2. a lower pitch
  3. a louder sound
Show answer

a louder sound A bigger amplitude and a louder sound.

Check 13

A loudspeaker is driven by a 440 Hz current. What is the frequency of the sound?

  1. 220 Hz
  2. 440 Hz
  3. 880 Hz
Show answer

440 Hz 440 Hz, the same as the current.

Check 14

A loudspeaker is driven at 500 Hz. How many times does the cone move back and forth in 2 seconds?

  1. 1000 times
  2. 250 times
  3. 502 times
Show answer

1000 times 500 × 2 = 1000 times.

Check 15

What does a microphone do?

  1. changes an electrical signal into sound
  2. makes sound louder
  3. changes sound into an electrical signal
Show answer

changes sound into an electrical signal It changes sound into an electrical signal.

Check 16

What vibrates when sound reaches a microphone?

  1. a big paper cone and a magnet
  2. a diaphragm with a coil on it
  3. a battery
Show answer

a diaphragm with a coil on it A thin diaphragm with a coil fixed to it.

Check 17

Which effect does a microphone use?

  1. the generator effect
  2. the motor effect
  3. reflection
Show answer

the generator effect The generator effect, where a potential difference is induced when a coil moves in a magnetic field.

Check 18

What is the generator effect?

  1. a force on a current in a field
  2. the heating of the air by a speaker
  3. a potential difference induced by moving a conductor in a magnetic field
Show answer

a potential difference induced by moving a conductor in a magnetic field A potential difference is induced when a conductor moves in a magnetic field.

Check 19

Is the signal from a microphone direct or alternating?

  1. direct
  2. alternating
  3. neither
Show answer

alternating It is alternating, because the coil moves back and forth.

Check 20

Why can a loudspeaker work as a simple microphone?

  1. sound moves the coil, so a potential difference is induced
  2. its magnet makes electricity on its own
  3. its cone makes light
Show answer

sound moves the coil, so a potential difference is induced Sound moves the cone and coil, so a potential difference is induced.

Check 21

Does the size of the current change the pitch of a loudspeaker note?

  1. yes, a bigger current gives a higher pitch
  2. yes, a bigger current gives a lower pitch
  3. no, it changes the loudness
Show answer

no, it changes the loudness No. The size changes the loudness, and the frequency changes the pitch.

Check 22

What is wrong with this: 'The magnet in a loudspeaker moves and pushes the air.'

  1. nothing is wrong
  2. the magnet is fixed, and the coil and cone move
  3. the magnet is made of paper
Show answer

the magnet is fixed, and the coil and cone move The magnet is fixed. The coil and the cone move.

Check 23

A student turns up the volume without changing the note. What changes in the current?

  1. its size gets bigger
  2. its frequency gets bigger
  3. it becomes a direct current
Show answer

its size gets bigger Its size, or amplitude, gets bigger, and the frequency stays the same.

Check 24

Which device is a motor effect device and which is a generator effect device?

  1. loudspeaker: generator effect, microphone: motor effect
  2. both use the motor effect
  3. loudspeaker: motor effect, microphone: generator effect
Show answer

loudspeaker: motor effect, microphone: generator effect A loudspeaker uses the motor effect and a microphone uses the generator effect.

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