- Electromagnetics I
- Ch 10: Appendices
- Loc 10.7

- Electromagnetics I
- Ch 10
- Loc 10.7

# Physical Constants

**The speed of light in free space** (

), which is the phase velocity of any electromagnetic radiation in free space, is

m/s. This is commonly rounded up to

m/s. This rounding incurs error of

%, which is usually much less than other errors present in electrical engineering calculations.

**The charge of an electron** is

C. The constant

C is known as the “elementary charge,” so the charge of the electron is said to be

.

**The permittivity of free space** (

) is

F/m.

**The permeability of free space** (

)

H/m.

**The wave impedance of free space** (

) is the ratio of the magnitude of the electric field intensity to that of the magnetic field intensity in free space and is

. This is also sometimes referred to as the *intrinsic impedance of free space*.

Ellingson, Steven W. (2018) Electromagnetics, Vol. 1. Blacksburg, VA: VT Publishing. https://doi.org/10.21061/electromagnetics-vol-1 CC BY-SA 4.0

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