Edexcel A Level Physics:复习笔记7.2 Electric Field Strength

• The electric field strength at a point is defined as:

The force per unit charge acting on a positive test charge at that point

• The electric field strength can be calculated using the equation:

• Where:
• • E = electric field strength (N C–1)
  • F = electrostatic force on the charge (N)
  • Q = charge (C)
• It is important to use a positive test charge in this definition, as this determines the direction of the electric field
• Recall, the electric field strength is a vector quantity, it is always directed:
  • Away from a positive charge
  • Towards a negative charge
• This direction is also denoted by the direction of the electric field

Electric field lines are directed away from a positive point charge and towards a negative point charge