| Definition/Meaning | Word/Phrase |
|---|---|
| transformer that supplies high voltage to spark plugs in a gasoline engine | coil |
| transformer that reduces voltage | step-down transformer |
| transformer that increases voltage | step-up transformer |
| step-up transformer with an air core; used to produce high voltages at high frequencies | Tesla coil |
| transformer whose voltage ratio of transformation can be adjusted | voltage regulator |