Electric Field Strength 2

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A Uniform Electric Field

A uniform field is one which has the same strength at every point in the field.

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Uniform field

  • A uniform field has the same strength everywhere, it can be made from parallel charged plates.
  • If two charged plates are held a distance apart the field between them will be uniform
    • The field lines will travel straight from the positive plate into the negative plate.
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Calculating the field

  • If two plates are held apart with different charges they will have a voltage difference between them. The equation for the field strength is:
    • Field strength = voltage drop ÷ distance between the plates
    • E=V/dE=V/d

Work done in an Electric Field

Two oppositely charged parallel plates provide a uniform electric field. Uniform fields have field lines that are equally spaced, straight and parallel.

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Moving between charged plates

  • The work done in moving a positively charged particle from the negative plate to the positive plate is:
    • W=F×dW= F \times d
  • Where F is a constant force acting on the charged particle and d is the separation of the plates.
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  • The work done in moving a positively charges particle is also, by definition:
    • W=Q×ΔVW = Q \times \Delta V
  • These two expressions are equal to each other:
    • F×d=Q×ΔVF\times d=Q\times \Delta V
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Derivation 2

  • Rearranging this gives:
    • FQ=ΔVd\frac{F}{Q}=\frac{\Delta V}{d}
  • Because FQ\frac{F}{Q} is defined as electric field strength, electric field strength between two parallel plates is:
    • E=ΔVdE = \frac{\Delta V}{d}

Jump to other topics

1Measurements & Errors

2Particles & Radiation


4Mechanics & Materials


6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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