Correcting Units (Edexcel International A Level (IAL) Physics): Revision Note

Correcting Units

• In Physics, a value without its appropriate unit doesn't really mean anything

  • For example, 5 mm or 5 km are very different measurements

• Some common units in A-level Physics are:

Common Units Table

• Sometimes practical questions require identifying units that are incorrect

• Learning the appropriate unit for each physical quantity in A-level physics is extremely important

• Sometimes the unit can be derived from an equation for that quantity

  • For example, the units of the resistivity ρ can be considered from its equation

ρ = $\frac{RA}{L}$

• Where:

  • R = resistance (Ω)

  • A = area (m²)

  • L = length (m)

• Therefore:

[ρ] = $\frac{\left[R\right]\left[A\right]}{\left[L\right]}$ =  $\frac{\Omega m^2}{m}$ = Ωm

• Common units for measurements are:

  • Length = m 

  • Area = m²

  • Volume = m³