A primary and secondary coil of wire wrapped around an iron core
* an iron core is used because it is easily magnetised
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How does a transformer work?
- An alternating current flows through the primary coil
- This induces a changing magnetic field in the core
- This induces an emf and produces a current in the secondary coil
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Why does the current flowing through the primary coil have to be alternating?
- In order for a current to be induced in the secondary coil, the magnetic field must be continuously changing
- To continuously change the magnetic field, the primary coil should have an alternating current flowing through
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When the transformer is 100% efficient, what are the inputs and outputs like?
The electrical power input is equal to the electrical power output
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What is the equation for transformers' p.d. using the number of turns in each coil?
V (primary) x I (primary)
=
V (secondary) x I (secondary)
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How many relative turns are in each coil of a step-up transformer?
The primary coil has less turns
The secondary coil has more turns
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Why are step-up transformers used?
- Found at power stations
- They are needed in transmission through power lines
- By increasing the voltage, the current is reduced which means less energy is lost by heating
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How many relative turns are in each coil of a step-down transformer?
- The primary coil has more turns
- The secondary coil has less turns
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Why are step-down transformers used?
- Found nearby domestic buildings
- Voltage is reduced to a safe level to be used in homes
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When does electromagnetic induction/the generator effect occur?
When there is relative movement between an electrical conductor and a magnet as the conductor cuts through the magnetic field
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What occurs when EM induction/the generator effect happens?
A p.d. is induced across the conductor
* If the conductor forms a closed loop or is part of a complete circuit, then a current is also induced.
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How does a dynamo (direct current generator) work?
- A coil of wire rotates in a magnetic field
- A split ring commutator is used so the coil moves in the same direction and also keeping the current flowing in the same direction
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How does an alternator (alternating current generator) work?
- A coil of wire rotates in a magnetic field
- Slip rings are used which causes the current to flow in a different direction as the coil rotates
- An alternating current is produced
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How does a microphone work?
- It uses the generator effect
- Pressure variations in sound waves are converted into an alternating current
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How does a loudspeaker work?
- It contains a coil of current flowing wire in a permanent magnet's field which leads to the motor effect
- The alternating current causes the force experienced by the wire to move back and forth, creating pressure variations/vibrations
- Audible sound i
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Other cards in this set
Card 2
Front
How does a transformer work?
Back
- An alternating current flows through the primary coil
- This induces a changing magnetic field in the core
- This induces an emf and produces a current in the secondary coil
Card 3
Front
Why does the current flowing through the primary coil have to be alternating?
Back
Card 4
Front
When the transformer is 100% efficient, what are the inputs and outputs like?
Back
Card 5
Front
What is the equation for transformers' p.d. using the number of turns in each coil?
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