ASRJC Electric Field Notes

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 Additional Notes Topic 13 Electric Fields Content A Concept of an electric field B Electric force between point charges C Electric field of a point charge D Uniform electric fields E Electric potential Learning Outcomes Candidates should be able to: (a) show an understanding of the concept of an electric field as an example of a field of force and define electric field strength at a point as the electric force exerted per unit positive charge placed at that point. (b) represent an electric field by means of field lines. (c) recognise the analogy between certain qualitative and quantitative aspects of electric and gravitational fields. (d) recall and use Coulomb’s law in the form 2 21 04 1 r QQF = for the force between two point charges in free space or air. (e) recall and use E = 2 04 1 r Q  for the field strength of a point charge in free space or air. (f) calculate the electric field strength of the uniform field between charged parallel plates in terms of potential difference and plate separation. (g) calculate the forces on charges in uniform electric field. (h) describe the effect of a uniform electric field on the motion of charged particles. (i) define electric potential at a point as the work done per unit positive charge in bringing a small test charge from infinity to that point. (j) state that the field strength of the field at a point is numerically equal to the potential gradient at that point. (k) use the equation 04 QV r= for the electric potential in the field of a point charge, in free space or air. Name: ________________________________ ( ) Class: 25 / ___

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 13-2 Additional Notes A Concept of an electric field Candidates should be able to: (a) show an understanding of the concept of an electric field as an example of a field of force and define electric field strength as force per unit positive charge. (b) represent an electric field by means of field lines. A.1 Concept of an electric field: Many everyday forces are pushes or pulls between bodies in contact. In other cases forces arise between bodies that are separated from one another (action- at-a-distance forces). An action-at-a-distance effect in which one body A exerts a force on another body B not in contact with it, can be regarded as due to a 'field of force' (or simply field) in the region around A. Field of force is a region of space where a body experiences a force. A.2 Definition of electric field: An electric field is a region of space where a stationary charge experiences a force. The direction of the electric field is the direction of the force on a positive charge. Note: The definition is in terms of the force on a stationary charge. A force on a moving charge could indicate that a magnetic field is present. A.3 Electric fiel