3. Surface shape o(r E 4 丌E 4. Volume shape E 4 2 丌 Discussion: Although the introduction of Field intensity has greatly simplified the theory, in practice, vector calculation is still not that easy People hope the scalar can be used in analyzing the electric field Therefore, the chain will be: Electric field- Electric field intensity-??(?? Should be a scalar It is the time back to mathematics 1.2. 3 Brief Review of Vector Theory3. Surface shape: ds r E r r o o s    2 ( ) 4 1     = 4. Volume shape: dv r E r r o o v    2 ( ) 4 1     = Discussion: Although the introduction of Field intensity has greatly simplified the theory, in practice, vector calculation is still not that easy. People hope the scalar can be used in analyzing the electric field. Therefore, the chain will be: Electric field → Electric field intensity→ ?? (?? Should be a scalar) It is the time back to Mathematics 1.2.3 Brief Review of Vector Theory