20.6 - How Transformers Work
What a transformer is made of
- A transformer is a device used to change the size of an alternating voltage.
- Every transformer has three main parts:
- A primary coil, which the input voltage is connected across.
- A secondary coil, which provides the output voltage.
- An iron core, which both coils are wound around.
- The two coils are not joined electrically - there's no wire connecting them.
- The iron core links the two coils magnetically.
Step-up and step-down transformers
- The number of turns on each coil decides whether the voltage increases or decreases:
- Step-up transformer - Increases the voltage. It has more turns on the secondary coil than the primary, so output voltage is greater than input voltage.
- Step-down transformer - Decreases the voltage. It has more turns on the primary coil than the secondary, so output voltage is smaller than input voltage.
- The coil with more turns has the larger voltage across it.
TermDefinition
TransformerA device that changes the size of an alternating potential difference (voltage).
Primary coilThe coil in a transformer that the input voltage is connected across.
Secondary coilThe coil in a transformer that provides the output voltage.
Step-up transformerA transformer that increases the potential difference (voltage) and decreases the current. It has more turns on its secondary coil than on its primary coil.
Step-down transformerA transformer that decreases the potential difference (voltage) and increases the current. It has fewer turns on its secondary coil than on its primary coil.