Electric field strength at a point is defined as the force per unit charge experienced by a small positive charge placed at the point.

An electric field is a region due to the presence of one or more charged bodies (known as the source). When a body (of charge q) is placed in this field, it experiences a force given by F = qE where E is the field strength at the point where the body is placed.

Electric potential at a point is defined as the work done in bringing a small unit positive charge from infinity to the point.

Electric field strength is a vector quantity. (-ve sign need not be substituted in formula during calculation. Direction of E (or net E) is determined from a diagram)

Electric potential is a scalar quantity. (-ve sign must be substituted in formula during calculation)

Due to a spherical or point charge in free space

Due to parallel charged plates

E=V/d (uniform field) [V is the pd between the plates and d the distance between them.]

Potential at a point (distance x from the lower potential plate, Vo) = Ex + Vo = Ex when Vo is set to zero.

Force and Potential energy of a charged body, q placed at a point in a field

F = qE and PE = qV

When a charge, q is placed at r from a point charged source,

When a charge, q is placed at a distance x from the lower potential plate, Vo in parallel plates, F = qE = qV/d and PE = qVx = q(Ex + Vo) = qEx when Vo = 0.

Relationship between E and V

Coulomb force between 2 point or spherical charges, Q1 and Q2

Electric field vs Gravitational field

Please view your Sku lecture notes on this! :D

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