Electric Field Strength

Key Stage 5

Electric field strength is the force per unit charge exerted on a small positive test charge placed at a point in the field.

Electric field strength is given by the symbol 𝐸.
The unit of electric field strength is Newtons per Coulomb (N/C) or volts per metre (V/m).
The direction of the electric field is the direction of the force that would act on a positive test charge.
Electric fields can be represented by field lines; the density of these lines indicates the field strength.

Electric Field Strength is given by the general formula\[𝐸=\frac{𝐹}{𝑄}\]

Where,

𝐹 is the force experienced by a charge 'Q' in the field.

and

𝑄 is the charge in that field.

The Electric field strength around a point charge is given by\[𝐸=𝑘\frac{𝑄}{𝑟_2}\]

Where:

𝑄 is the point charge causing the field

and

𝑟 is the distance from that point charge

Since;

\(𝑘=\frac{1}{4\pi\varepsilon_0}\)

Then\[𝐸=\frac{1}{4\pi\varepsilon_0}\frac{𝑄}{𝑟_2}\]

or

\(𝐸=\frac{𝑄}{4\pi\varepsilon_0𝑟_2}\)

Where\[\varepsilon_0\] is the permittivity of free space