AQA A Level Physics复习笔记7.4.3 Electric Field Strength

• An electric field is a region of space in which an electric charge “feels” a force
• The electric field strength at a point is defined as:

The electrostatic force per unit positive charge acting on the 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
• The electric field strength is a vector quantity, it is always directed:
  • Away from a positive charge
  • Towards a negative charge

   

• Recall that opposite charges (positive and negative) charges attract each other
• Conversely, like charges (positive and positive or negative and negative) repel each other