OCR · GCSE · Physics
Course version: J249 · Version from Sept 2018
Explain how transfer of electrons between objects can explain the…
Full specification wording
Static and charge: explain how transfer of electrons between objects can explain the phenomena of static electricity
Static electricity arises because electrons, which carry negative charge, can be moved from one object to another when two different insulating materials are rubbed together.
Checked against the OCR J249 specification (opens in a new tab) on .
- Point 4 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Static electricity arises because electrons, which carry negative charge, can be moved from one object to another when two different insulating materials are rubbed together. The object that gains electrons becomes negatively charged; the object that loses electrons is left with a deficit of negative charge and so becomes positively charged. The total charge is conserved, so the two objects always carry equal and opposite charges. A charged object can then attract small neutral objects such as scraps of paper, because the charged object repels or attracts electrons within the neutral object and induces a charge separation. Two objects carrying like charges repel; two carrying opposite charges attract. The electrons themselves do not travel through the air in these everyday effects; the charge stays on the surface of the insulator.
What earns the marks
- States that rubbing two different insulating materials transfers electrons from one object to the other.
- Identifies the object that gains electrons as becoming negatively charged and the object that loses electrons as becoming positively charged.
- Explains that the two objects end up with equal and opposite charges because charge is conserved.
- Explains attraction of a neutral object in terms of induced charge separation caused by the charged object.
- States that like charges repel and opposite charges attract, linking this to the observed forces.
Common mistakes and how to put them right
Claims that protons are transferred between the objects.
Put it right by stating that only electrons move between materials in static charging.
Says the object that gains electrons becomes positive.
Put it right by linking gain of negative electrons to a negative charge.
Describes electrons flowing through the air to a nearby object.
Put it right by explaining that the charge remains on the surface of the insulator and acts at a distance through the electric field.
Exam tips
- Name the particle that moves (electrons) and state the direction of transfer before describing the resulting charges.
- Use the words 'gain' and 'lose' electrons explicitly so the sign of each charge is unambiguous.
- When explaining attraction of a neutral object, mention induced charge separation rather than saying the neutral object is simply 'attracted for no reason'.
Try the lesson
The start of the Static and charge: explain how transfer of electrons between objects can explain the phenomena of static electricity lesson, made from checked teaching notes for this specification point.
Have a go first
A glass rod is rubbed with a silk cloth and becomes positively charged. What has happened to the glass rod?
Listen
Static electricity arises because electrons, which carry negative charge, can be moved from one object to another when two different insulating materials are rubbed together. The object that gains electrons becomes negatively charged; the object that loses electrons is left with a deficit of negative charge and so becomes positively charged. The total charge is conserved, so the two objects always carry equal and opposite charges. A charged object can then attract small neutral objects such as scraps of paper, because the charged object repels or attracts electrons within the neutral object and induces a charge separation. Two objects carrying like charges repel; two carrying opposite charges attract. The electrons themselves do not travel through the air in these everyday effects; the charge stays on the surface of the insulator. A strong answer earns marks for these points. States that rubbing two different insulating materials transfers electrons from one object to the other. Identifies the object that gains electrons as becoming negatively charged and the object that loses electrons as becoming positively charged. Explains that the two objects end up with equal and opposite charges because charge is conserved. Explains attraction of a neutral object in terms of induced charge separation caused by the charged object. A common slip: Claims that protons are transferred between the objects. Instead, stating that only electrons move between materials in static charging. Exam tip: Name the particle that moves (electrons) and state the direction of transfer before describing the resulting charges.
Key words
Say what each word means before you turn the card.
Conservation of charge
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Positive and negative charging by friction
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Forces between charged objects
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Charge carriers and transfer of electrons
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See every definition
- Conservation of charge
- The total charge is conserved, so the two objects always carry equal and opposite charges.
- Positive and negative charging by friction
- Rubbing two different insulating materials transfers electrons from one object to the other; the object that gains electrons becomes negatively charged and the object that loses electrons becomes positively charged.
- Forces between charged objects
- Two objects carrying like charges repel; two carrying opposite charges attract.
- Charge carriers and transfer of electrons
- Electrons, which carry negative charge, can be moved from one object to another when two different insulating materials are rubbed together.
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