AQA GCSE Physics

Revision Notes

2.4.4 Fields & Static

Fields & Static

  • Objects with static charge create an electric field in the space around them
    • If other charges enter the field then they will experience an electric force, attracting or repelling them from the object
  • Therefore, an electric field can be defined as:

A region in which a charged object will experience an electric force

  • Electric fields are represented by electric field lines that are always in the direction of positive to negative
  • The electric field lines for a charged, isolated sphere, such as a spherical conductor:
    • Point away from the centre of a positive sphere
    • Point towards the centre of a negative sphere

Point charge field lines, downloadable AS & A Level Physics revision notes

  • A uniform electric field, such as that between two parallel plates, are straight parallel lines from positive to negative:

parallel-plates, IGCSE & GCSE Physics revision notes

Electric field lines between two parallel plates

  • The electric field pattern between two oppositely charged spheres (or point charges) is slightly different and looks like:

Electric field pattern for two opposite charges

  • The electric field helps to explain the non-contact force between charged objects since the electric field cannot be seen, but can be detected by another charged object that moves within that field due to the electric force
    • This is a non-contact force because the charged objects do not touch for the force to be exerted
  • If an electric field becomes strong enough, the charges are forced through insulators such as air, creating a spark
    • This is what happens for example, when a charged person touches a conductor
  • The charged particles will travel towards areas with the opposite charge

fields-and-sparks, IGCSE & GCSE Physics revision notes

Positive and negative charges will travel towards the opposite charge, creating a spark

Exam Tip

Remember when drawing field lines to always include their direction with arrows pointing in the correct direction. If the field lines are straight, always use a ruler or a straight edge to draw them

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