SI prefix
Physical Quantities & Units - OCR A-Level Physics
Key Definition
SI prefix
A prefix attached to a unit to indicate a power of ten, making very large or very small numbers easier to express.
A prefix attached to a unit to indicate a power of ten, making very large or very small numbers easier to express.
- teraSI prefix meaning 10¹² (one trillion). Symbol: T. (T) = \(10^{12}\)
- gigaSI prefix meaning 10⁹ (one billion). Symbol: G. (G) = \(10^{9}\)
- megaSI prefix meaning 10⁶ (one million). Symbol: M. (M) = \(10^{6}\)
- kiloSI prefix meaning 10³ (one thousand). Symbol: k. (k) = \(10^{3}\)
- centiSI prefix meaning 10⁻² (one hundredth). Symbol: c. (c) = \(10^{-2}\)
- milliSI prefix meaning 10⁻³ (one thousandth). Symbol: m. (m) = \(10^{-3}\)
- microSI prefix meaning 10⁻⁶ (one millionth). Symbol: μ. ($\mu$) = $10^{-6}$
- nanoSI prefix meaning 10⁻⁹ (one billionth). Symbol: n. (n) = \(10^{-9}\)
- picoSI prefix meaning 10⁻¹² (one trillionth). Symbol: p. (p) = \(10^{-12}\)
Common Mistake
MEDIUM
Wrong: Using mm^2 or cm^2 directly in equations without converting to \(m^{2}\).
Right: 1 $mm = 10^{-3} m$, so 1 mm^2 = (\(10^{-3}\))^2 = \(10^{-6}\) \(m^{2}\). Square the conversion factor when dealing with area or volume.
Right: 1 $mm = 10^{-3} m$, so 1 mm^2 = (\(10^{-3}\))^2 = \(10^{-6}\) \(m^{2}\). Square the conversion factor when dealing with area or volume.