18. Electric fields
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18.1 Electric fields and field lines
18.1.1An electric field is an example of a field of force and define electric
• understand that an electric field is an example of a field of force and define electric field as force per unit positive charge
18.1.2F = qE for the force on a charge in an electric field
• recall and use F = qE for the force on a charge in an electric field
18.1.3An electric field by means of field lines
• represent an electric field by means of field lines
18.2 Uniform electric fields
• recall and use E = ∆V / ∆d to calculate the field strength of the uniform field between charged parallel plates
• describe the effect of a uniform electric field on the motion of charged particles
18.3 Electric force between point charges
• understand that, for a point outside a spherical conductor, the charge on the sphere may be considered to be a point charge at its centre
• recall and use Coulomb’s law F = Q1Q2 / (4πε0 r 2) for the force between two point charges in free space
18.4 Electric field of a point charge
• recall and use E = Q / (4πε0 r 2) for the electric field strength due to a point charge in free space
18.5 Electric potential
• define electric potential at a point as the work done per unit positive charge in bringing a small test charge from infinity to the point
• recall and use the fact that the electric field at a point is equal to the negative of potential gradient at that point
• use V = Q / (4πε0 r) for the electric potential in the field due to a point charge
• understand how the concept of electric potential leads to the electric potential energy of two point charges and use EP = Qq / (4πε0 r)