Electrostatic and Gravitational Fields of Force

• Electric Field Strength is the Force per unit Charge
• An electric field causes a force on a charged particle within its field. No force is generated unless there are two particles in a field.
• Electric Potential is the work done per unit charge in bringing a positive charge from infinity to that point.
• Electric Potential drops off with distance for a positive charge
• Electric Potential increases with distance for a negative charge
• An equipotential surface is a surface that has the same potential difference everywhere on it
• Gravitational field lines show the path a mass would take if it were placed in a gravitational field. We assume the mass is concentrated at the centre of the object. The direction is always toward the mass creating the field
• Newton's Universal Law of Gravitation


  Every particle of matter attracts every other particle of matter with force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
• Coloumb's Inverse Square Law

  The electrostatic force between small bodies is proportional to the product of their charges and inversely proportional to their separation squared
• Gravitational Field Strength

  The force experienced per unit mass by a point mass placed in the field
• Gravitational Potential

  The work done per unit mass in bringing a mass from infinity to that point