| English | Transformer |
|---|---|
| Bahasa Melayu | Transformer |
| 中文 | 变压器 |
Definition
A device that uses electromagnetic induction to change the voltage of an alternating current.
In exam terms
A transformer is a device that uses electromagnetic induction to change the voltage of an alternating current. It has a primary coil and a secondary coil wound on a common soft iron core; the changing current in the primary sets up a changing magnetic flux that induces an e.m.f. in the secondary.
For an ideal transformer the turns ratio equals the voltage ratio: V_p / V_s = N_p / N_s, where V is voltage in volts (V) and N is the number of turns. In an ideal transformer power is conserved, so V_p I_p = V_s I_s, with current I in amperes (A).
Example of correct use: A transformer with 1000 primary turns and 100 secondary turns steps 240 V down to 24 V.
Do not confuse it with…
Do not confuse a transformer with a rectifier. A transformer only changes the size of an alternating voltage and cannot work with steady direct current, while a rectifier changes alternating current into direct current.
A transformer needs a changing flux, which d.c. cannot provide.
In Paper 2 this is asked as calculate or explain: calculate the secondary voltage or current from the turns ratio, or explain why a transformer does not work with direct current. State clearly that d.c. gives a steady flux, so no e.m.f. is induced in the secondary.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)