AQA GCSE Physics

Revision Notes

2.4.3 Electric Fields

Electric Fields

  • A charged object creates an electric field around itself
    • This is similar to the way in which magnets create magnetic fields
  • This can be shown by electric field lines
  • Fields lines always point away from positive charges and towards negative charges

electric-fields, IGCSE & GCSE Physics revision notes

Electric fields are always directed away from positive charges and towards negative charges

  • The strength of an electric field depends on the distance from the object creating the field:
    • The field is strongest close to the charged object – this is shown by the field lines being closer together
    • The field becomes weaker further away from the charged object – this is shown by the field lines becoming further apart

Electric Forces in a Field

  • Objects in an electric field will experience an electric force
    • Since force is a vector, the direction of this force depends on whether the charges are the same or opposite
  • The force is either attractive or repulsive
    • If the charges are the same (negative and negative or positive and positive), this force will be repulsive and the second charged object will move away from the charge creating the field
    • If the charges are the opposite (negative and positive), this force will be attractive and the second charged object will move toward the charge creating the field

field-and-force, IGCSE & GCSE Physics revision notes

When the negative particle enters the electric field, it feels a force of attraction towards the positive charge

  • The size of the force depends on the strength of the field at that point
  • This means that the force becomes:
    • Stronger as the distance between the two charged objects decreases
    • Weaker as the distance between the two charged objects increases
  • The relationship between the strength of the force and the distance applies to both the force of attraction and force of repulsion
    • Two negative charges brought close together will have a stronger repulsive force than if they were far apart

Electric Force and Distance, downloadable IGCSE & GCSE Physics revision notes

Repulsive forces decrease as like charges move further apart

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