| English | Direct current |
|---|---|
| Bahasa Melayu | Arus terus |
| 中文 | 直流电 |
Definition
An electric current that flows in one direction only.
In exam terms
Direct current (d.c.) is an electric current that flows in one direction only. Current is measured in amperes (A).
On a current-time graph, a steady direct current is shown as a horizontal line that stays on one side of the time axis.
Direct current is supplied by cells and batteries, and it is what most electronic circuits use internally. Because the direction never reverses, one terminal stays positive and the other stays negative.
Example of correct use: The 1.5 V dry cell drives a direct current through the torch bulb in a single direction. An alternating current can be converted to direct current using a rectifier.
Do not confuse it with…
Do not confuse direct current with alternating current (a.c.). Alternating current reverses direction regularly and its current-time graph crosses the time axis, while direct current keeps one direction and stays on one side of the axis.
Only alternating current can be used with a transformer.
In Paper 2 this is asked as define or compare: define direct current, or compare the current-time graphs of d.c. and a.c. When comparing, state that d.c. is one-directional (a straight horizontal line) and a.c. is bidirectional (a curve crossing the axis).
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)