Static Electricity

    OCR
    GCSE

    Static electricity arises from the transfer of electrons between electrical insulators through friction, resulting in a net positive or negative charge on the material. This accumulation of charge creates an electric field in the surrounding space, exerting non-contact electrostatic forces of attraction or repulsion on other charged or neutral objects. When the potential difference between a charged object and an earthed point exceeds the dielectric strength of air, rapid discharge occurs in the form of a spark. Understanding these principles is essential for explaining phenomena ranging from lightning strikes to industrial applications like electrostatic precipitation.

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    Objectives
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    Exam Tips
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    Pitfalls
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    Key Terms
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    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that friction causes the transfer of electrons from one insulator to another
    • Credit responses that explicitly state protons (or positive charges) do not move; charge is created by electron loss or gain
    • Award 1 mark for drawing electric field lines perpendicular to the surface and directed away from positive charges (or towards negative)
    • For sparking (Higher Tier), candidates must link high potential difference to the ionization of air molecules allowing charge to flow
    • Award 1 mark for identifying that a charged object induces a charge separation in a nearby neutral conductor

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified that friction charges the object, but you must specify that *electrons* are transferred, not just 'charge'."
    • "Your field lines are the correct shape, but remember they must have arrows pointing away from positive charges and towards negative ones."
    • "Good explanation of repulsion. To improve, explicitly mention the 'non-contact force' generated by the interacting electric fields."
    • "You mentioned a spark occurs; for higher marks, explain *why* the air becomes conductive (ionization due to high potential difference)."

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that friction causes the transfer of electrons from one insulator to another
    • Credit responses that explicitly state protons (or positive charges) do not move; charge is created by electron loss or gain
    • Award 1 mark for drawing electric field lines perpendicular to the surface and directed away from positive charges (or towards negative)
    • For sparking (Higher Tier), candidates must link high potential difference to the ionization of air molecules allowing charge to flow
    • Award 1 mark for identifying that a charged object induces a charge separation in a nearby neutral conductor

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When describing charging, always name the particle (electron) and the direction of transfer (e.g., 'electrons move from the cloth to the rod').
    • 💡In 3-mark questions on electric shocks, structure your answer: Charge build-up → Potential difference increases → Discharge/Current flows through person to earth.
    • 💡For electric field diagrams, ensure lines are evenly spaced to represent a uniform field, or spread out to show a weakening field; spacing equals strength.

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Suggesting that positive charges or protons move to create a positive charge on an object
    • Drawing electric field lines that cross one another or fail to touch the surface of the charged object
    • Confusing the mechanism of earthing; stating charge 'disappears' rather than electrons flowing to or from the ground to neutralise the object
    • Describing the force between charged objects without using the term 'non-contact force' or 'electrostatic force'

    Study Guide Available

    Comprehensive revision notes & examples

    Read Study Guide

    Key Terminology

    Essential terms to know

    Charging by friction and electron transfer
    Electrostatic forces (attraction and repulsion)
    Electric fields and field line representation
    Electrical discharge and sparking mechanisms

    Likely Command Words

    How questions on this topic are typically asked

    Describe
    Explain
    Draw
    Predict
    Compare

    Practical Links

    Related required practicals

    • •{"code":"PAG P3","title":"Investigation of static electricity","relevance":"Testing insulating materials using rods (polythene/acetate) and cloths to observe attraction/repulsion"}

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