| English | Ohm's law |
|---|---|
| Bahasa Melayu | Hukum Ohm |
| 中文 | 欧姆定律 |
Definition
The current through a conductor is directly proportional to the potential difference across it, provided its temperature stays constant.
In exam terms
Ohm’s law states that the current I through a conductor is directly proportional to the potential difference V across it, provided the temperature stays constant. This gives the working relationship V = IR, where R is the resistance, measured in ohms (Ω).
A conductor that obeys this law is called an ohmic conductor, and its V–I graph is a straight line passing through the origin.
Example of correct use: a 6 Ω resistor carrying a current of 2 A has a potential difference of V = IR = 2 A × 6 Ω = 12 V across it.
Do not confuse it with…
Do not confuse Ohm’s law with the definition of resistance. The equation R = V/I defines resistance for any component, but Ohm’s law only holds when the temperature is constant, so that R itself stays constant.
A filament lamp is non-ohmic: as current heats the filament, its resistance rises and the V–I graph curves.
In Paper 2, if asked to state Ohm’s law you must give both the proportionality between current and potential difference and the constant-temperature condition; leaving out the condition loses the mark.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)