| English | Electrical energy |
|---|---|
| Bahasa Melayu | Tenaga elektrik |
| 中文 | 电能 |
Definition
The energy transferred by an electric current, equal to power multiplied by time; measured in joules (J).
In exam terms
Electrical energy is the energy transferred by an electric current as it flows through a component. It is measured in joules (J) and can be found from E = Pt = VIt, and for a resistor also as E = I²Rt or E = V²t/R. Household bills use a larger commercial unit, the kilowatt-hour (kWh).
Example of correct use: an appliance rated 1000 W run for 60 s transfers electrical energy of E = Pt = 1000 W × 60 s = 60 000 J.
Do not confuse it with…
Do not confuse electrical energy with electrical power. Energy is the total amount transferred, measured in joules; power is the rate of transfer, measured in watts (1 W = 1 J s⁻¹).
Energy equals power multiplied by time, so a low-power device left on for a long time can still use a large amount of energy.
In Paper 2, questions often ask you to calculate the energy used or the cost of running an appliance; be careful to convert time to seconds for joules, or to hours for kilowatt-hours.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)