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The numerical values of a few important constants are listed.
Important Constants
We will follow the SI system of units. In SI units, the constants $\epsilon_0$ and $\mu_0$ appear in the basic equations of electromagnetism. These constants are determined from experiments. For example \(\epsilon_0\) could be determined by measurement of Coulomb force between two charges. Similarly, \(\mu_0\) can be determined by a measurement of magnetic force between current carrying wires. In Table 1, the numerical values of some constants are listed.
| Table 1: Important constants | ||
| Mass of electron | \(9.11\times 10^{-31} \text{kg}\) | |
| Charge of electron | \(e= 1.60\times 10^{-19} \text{C}\) | |
| Velocity of light | \(c = 2.998\times 10^8 \text{m/s}\) | |
| Permittivity of free space | \(\epsilon_0=8.854 \times 10^{-12}\) C\(^2\)/(N. m \(^2\)) | |
| Permeability of free space | \(\mu_0=4 \pi \times 10^{-7}\) Wb/(A.m) | |
For numerical computations, it will be sufficient to round off the numerical values of the constants as follows.
\begin{eqnarray} \nonumber\frac{1}{4\pi\epsilon_0}&=& 9\times10^{9}\, \text{Nm}^2/\text{C}^2 \\ \nonumber\frac{\mu_0}{4\pi}&=&10^{-7}\, \text{Wb/(A} \cdot \text{m)}\\ \nonumber c &=&3\times10^{8}\, \text{m/s}. \end{eqnarray}
