Induced potential, transformers and the national grid Flashcards
What happens when an electrical conductor moves through a magnetic field?
A potential difference is induced across the ends of the conductor. If the conductor is part of an electric circuit, an induced current will flow.
The direction of current switches when the direction of movement switches.
What happens to an electrical conductor when a magnetic field moves through it?
A potential difference is induced across the ends of the conductor. If the conductor is part of an electric circuit, an induced current will flow.
The direction of current switches when the direction of movement switches.
What is the requirement for an induced potential difference to cause a current flow?
The conductor must form a closed loop or be part of a complete circuit.
What can be said about the direction of the magnetic field produced by an induced current?
- The direction of the field is such that it opposes the change that induced the current.
- This change is either the movement of the conductor or of the magnetic field.
What are the 2 ways that the generator effect is used to generate different types of current?
- In an alternator to produce alternating-current.
- In a dynamo to produce direct-current.
What electromagnetic effect does a microphone take advantage of and how?
- The generator effect.
- It converts the pressure variations in sound waves into alternating current in a circuit.
Describe the makeup of a basic transformer
A primary coil and a secondary coil wire wrapped around an iron core.
Why is iron used as the core for a transformer?
It is easily magnetised.
Explain how a transformer works
- An alternating current flows through the primary coil.
- This induces a changing magnetic field which is transmitted along the iron core.
- This changing magnetic field induces a potential difference and current through the secondary coil.
Why must the current flowing through the primary coil of a transformer be alternating?
- For current to be induced in the secondary coil, the magnetic field in the core must be continuously changing.
- For the magnetic field to be changing, the current in the primary coil must be alternating.
What can be said about the electrical power input and output of a 100% efficient transformer?
The electrical power input is equal to the electrical power output.
How does an alternator work?
As one side of the coil moves up through the magnetic field, a potential difference is induced in one direction. As the rotation continues and that side of the coil moves down, the induced potential difference reverses direction. This means that the alternator produces a current that is constantly changing. This is alternating current or ac. A slip ring commutator is used.
How does a dynamo work?
In a dynamo, a split ring commutator changes the coil connections every half turn. As the induced potential difference is about to change direction, the connections are reversed. This means that the current to the external circuit always flows in the same direction.
How can you increase maximum potential difference in a dynamo and alternator?
- Increasing the rate of rotation.
- Increasing the strength of the magnetic field.
- Increasing the number of turns on the coil.
How does a microphone work?
1) Pressure variations in sound waves cause the flexible diaphragm to vibrate.
2) The vibrations of the diaphragm cause vibrations in the coil.
3) The coil moves relative to a permanent magnet, so a potential difference is induced in the coil.
4) The coil is part of a complete circuit, so the induced potential difference causes a current to flow around the circuit.
5) The changing size and direction of the induced current matches the vibrations of the coil.
6) The electrical signals generated match the pressure variations in the sound waves.
