Electric Potential (OCR A Level Physics)

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Electric Potential

  • In order to move a positive charge closer to another positive charge, work must be done to overcome the force of repulsion between them
    • Similarly, to move a positive charge away from a negative charge, work must be done to overcome the force of attraction between them

  • Energy is therefore transferred to the charge that is being pushed upon
    • This means its potential energy increases

  • If the positive charge is free to move, it will start to move away from the repelling charge
    • As a result, its potential energy decreases back to 0

  • This is analogous to the gravitational potential energy of a mass increasing as it is being lifted upwards and decreasing as it falls
  • The electric potential at a point is defined as:

The work done per unit positive charge in bringing a point test charge from infinity to a defined point

  • Electric potential is a scalar quantity
    • This means it doesn’t have a direction

  • Even though electric potential is a scalar quantity, it can take a positive or negative sign, this is because the electric potential is:
    • Positive around an isolated positive charge
    • Negative around an isolated negative charge
    • Zero at infinity

  • Positive work is done by the mass from infinity to a point around a positive charge and negative work is done around a negative charge. This means:
    • When a positive test charge moves closer to a negative charge, its electric potential decreases
    • When a positive test charge moves closer to a positive charge, its electric potential increases

  • To find the potential at a point caused by multiple charges, the total potential is the sum of the potential from each charge

Electric Potential around Positive & Negative Charges 1, downloadable AS & A Level Physics revision notesElectric Potential around Positive & Negative Charges 2, downloadable AS & A Level Physics revision notes

The electric potential V decreases in the direction the test charge would naturally move in due to repulsion or attraction

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Katie M

Author: Katie M

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

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