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 = 
- Where:
- R = resistance (Ω)
- A = area (m2)
- L = length (m)
- Therefore:
[ρ] = 
= 
= Ωm
- Common units for measurements are:
- Length = m
- Area = m2
- Volume = m3
Worked example
Correct the following incorrect units:
- Magnetic Flux Density = 2 Webers
- Electromotive Force = 7.8 N
- Capacitance = 0.3 µC
- Stress = 600 m2
The correct units are:
-
- Magnetic Flux Density = 2 T (Tesla)
- Electromotive Force = 7.8 V (Volts)
- Capacitance = 0.3 µF (Micro-farads)
- Stress = 600 Pa (Pascals)
