Paper 2 Knowledge Gaps: Content Flashcards
What are the different types of generators?
- alternators
- dynamos
What current does an alternator produce?
Alternating current
What current does a dynamo produce?
Direct Current
What is the difference between the parts of an alternator and the parts of a dynamo?
- alternators have slip rings and brushes
- dynamos have split ring commutators
Describe how an alternator works
- The coil of wire rotates relative to the magnets,
- this induces a magnetic field in the coil
- which then induces a voltage and current in the coil.
- as the coil rotates faster, the peaks of the oscillation get larger and more frequent
What is the role of a slip ring in an alternator?
- the contacts don’t swap every half turn
- so an alternating current is produced
How do dynamos work?
- As the coil of wire spins relative to the magnet, a magnetic field is induced
- so, a voltage and current are induced in the coil.
- as the coil rotates faster, the oscillations get larger and more frequent
What is the role of the split ring commutator in a dynamo?
- contacts swap every half turn
- so the current is always flowing in the same direction
- producing a direct current
What do loudspeakers do?
Take electrical signals and use the motor effect to convert them into vibrations, which then generate sound waves
What do microphones do?
Detect vibrations caused by sound waves and convert them into electrical signals
What current do loudspeakers and microphones use?
alternating current
What effect do loudspeakers and microphones use?
Motor effect
How does a loudspeaker work?
- A.C. flows through wire and creates a magnetic field
- this magnetic field of the coil interacts with the magnetic field of the permanent magnet in the loudspeaker
- interacting magnetic fields exert a force onto the coil and cause it to move back and forth
- the cone will change shape
- as current is alternating, the magnetic field and the force experienced is also alternating, so the coil of wire and cone rapidly vibrate
- vibrations are so fast that the cone vibrations cause pressure variations in the air - sound waves are produced
How does a microphone work?
- sound waves hit the diaphragm
- diaphragm and coil of wire move
- wire is moving within the magnetic field of the permanent magnet = current generated
What determines the frequency and amplitude of the current produced in a sound wave?
the frequency and amplitude of sound waves