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electric field
1. Two laws
(1) The law of conservation of electric charge: the charge is neither created nor destroyed, it can only be transferred from one object to another, or from one part of the object to another;
(2) Coulomb's law
①＝k
, r is the distance between two charges. For two uniformly charged balls that can be regarded as point charges, r is the distance between the two spheres.
(2) When the distance between two charges is →0, the charge cannot be regarded as a point charge, and the electrostatic force between them cannot be considered to tend to infinity.
2. The nature of the force of the electric field
3. The nature of the energy of the electric field
4. The relationship between the potential difference and the strength of the electric field
(1) The relationship between the potential difference and the field strength in a uniform electric field: UAB=Ed, where d is the distance between two points in the electric field.
(2) The direction and magnitude of the electric field strength: the electric potential decreases the fastest along the direction of the electric field strength. In a uniform electric field, the field strength is numerically equal to the potential that decreases per unit distance in the direction.
(3) The field strength is determined by the known three-point electric potential
| Division | Parallel conclusion method | Orthogonal decomposition method |
| | | |
| The potential difference between two segments of the same line in a uniform electric field is proportional to the length of the line segment. | If the two segments are parallel in a uniform electric field, the potential difference between the two segments is proportional to the length of the segments. This method can be used when parallel lines appear in the problem. | In the uniform electric field, E=U/d is used to find the field strengths in the two vertical directions, and then the combined field strengths are obtained. This method can only be used if it is vertical. |
5. The distribution law of electric field intensity and electric potential of the electric field of the isometric point charge
| electric field | Equipotential surface (solid line) | E-x | φ-x |
| Isometric differences Electricity charge of electricity field | | | |
| | Connect the perpendicular line on each point potential Equal and zero | ||
| The same amount Positive point charged electric field | | | |
| | |
6. Image problems in electric fields
| φ-x image | E-x images | EP-x image |
| | | |
| Slope: The strength of the electric field | Area: Potential difference | Slope: Electric field force |
7. I-t diagram, Q-t diagram and U-t diagram during capacitor discharge
| I-t diagrams | Q-t diagram | U-t diagram |
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