Electric Field Strength
The electric field strength of a uniform field between two charged parallel plates is defined as:
$
\mathrm{E}=\frac{\Delta V}{\Delta d}
$
- Where:
- $\mathrm{E}=$ electric field strength $\left(\mathrm{V} \mathrm{m} \mathrm{m}^{-1}\right)$
- $\Delta \mathrm{V}=$ potential difference between the plates $(\mathrm{V})$
- $\Delta \mathrm{d}=$ separation between the plates $(\mathrm{m})$
- Note: the electric field strength is now also defined by the units $\mathbf{V} \mathbf{m}^{-1}$
- The equation shows:
- The greater the voltage between the plates, the stronger the field
- The greater the separation between the plates, the weaker the field
- Remember this equation cannot be used to find the electric field strength around a point charge (since this would be a radial field)
- The direction of the electric field is from the plate connected to the positive terminal of the cell to the plate connected to the negative terminal
- Note: if one of the parallel plates is earthed, it has a voltage of $0 \mathrm{~V}$