Magnetism and electromagnetism units
- Syllabus
- 2024
- Topic
- —
- Level
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Learning objectives
Use ampere, volt and watt correctly
An electrical measurement needs a number and the unit for the quantity being measured. In magnetism and electromagnetism, use ampere for current, volt for voltage and watt for power.
| Physical quantity | Unit name | Unit symbol | Example reading |
|---|---|---|---|
| electric current | ampere | A | 2.5 A |
| voltage (potential difference) | volt | V | 12 V |
| power | watt | W | 60 W |
Read each value as a complete measurement: 2.5 A means a current of 2.5 amperes, 12 V means a voltage of 12 volts, and 60 W means a power of 60 watts. Identify the physical quantity first, then attach its matching unit symbol to the numerical value.
The unit symbols are capital letters and are not interchangeable: A does not mean voltage, V does not mean power, and W does not mean current. Do not add a degree sign, plural ending or full stop to a symbol: write 3 A, 6 V and 20 W.