(A Level) Electric fields

Learning objectives

Define electric field strength as force per unit positive charge, use F = qE, and draw field lines for point charges, pairs of charges and charged parallel plates.

Calculate the uniform field between parallel plates with E = ΔV/Δd, and describe the parabolic path of a charged particle that enters the field at right angles to it.

Use Coulomb's law F = Q₁Q₂/(4πε₀r²) and the point-charge field E = Q/(4πε₀r²), modelling a charged conducting sphere as a point charge at its centre.

Define the electric potential at a point as the work needed per coulomb to bring a small positive test charge there from infinity, use V = Q/(4πε₀r), and link field strength to potential gradient with E = −ΔV/Δx.

Use Ep = Qq/(4πε₀r) for the potential energy of a pair of point charges, and compare electric fields with gravitational fields.