Electric Fields

Define Electric field

Sketch electric field line

One for positive

One for negative

Sketch electric field line Between a positive and a negative charge

Electric fields flow from

Positive to negative

Define electric field strength and give the equation

Derive the equation for electric field strength

Define electric potential and give equation

Equation for electric field strength between two parallel plates

Compare motion in an electric field and gravitational field

1. Force

   BOTH fields exert forces that cause objects to accelerate:

• The force in an

  electric field is F = qE,

  gravitational field it is F = mg.

• Electric force can act upwards or downwards, depending on the sign of the charge.

• Gravitational force always acts downwards on mass

2. Acceleration

• electric field is a = qE/m and depends on the charge and field strength.

  gravitational field, is a = g, which is constant near Earth.

• Both fields do work when moving an object through a distance, changing its potential energy:
  

  • Electric: ΔPE = qΔV

  • Gravitational: ΔPE = mgΔh

• In a uniform field, motion is uniformly accelerated in both cases.

Prove the equation for electric potential energy in terms of electric fields