| English | Step-down transformer |
|---|---|
| Bahasa Melayu | Transformer injak turun |
| 中文 | 降压变压器 |
Definition
A transformer with fewer turns on the secondary coil than the primary, which decreases the alternating voltage.
In exam terms
A step-down transformer has fewer turns on the secondary coil than on the primary coil (N_s < N_p), which decreases the alternating voltage from primary to secondary. Voltage is measured in volts (V).
Since V_s / V_p = N_s / N_p and power is conserved in an ideal transformer (V_p I_p = V_s I_s), a lower output voltage comes with a larger output current. Example of correct use: A step-down transformer with 2400 primary turns and 120 secondary turns lowers 240 V to 12 V for a low-voltage lamp. Step-down transformers are used near homes and in chargers to reduce the grid voltage to safe, usable levels.
Do not confuse it with…
Do not confuse a step-down transformer with a step-up transformer. A step-down transformer has fewer secondary turns and lowers the voltage; a step-up transformer has more secondary turns and raises it.
The device is the same in principle, only the turns ratio decides the effect.
In Paper 2 this appears as state or calculate: state whether the transformer steps down and by what factor, or calculate the reduced output voltage. When answering, confirm N_s < N_p, then apply the turns ratio to find the smaller voltage.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)