all electric field lines start on positive charges. explain why this makes sense.
The statement that all electric field lines start on positive charges is a fundamental concept in electrostatics. It is known as the principle of electric field line behavior.
To understand why this concept makes sense, let's start with some background information. Electric field lines are imaginary lines representing the direction and strength of the electric field. They are used to visualize the behavior of electric fields, which are created by electric charges. The direction of an electric field line at any point indicates the direction in which a positive test charge would move if placed at that location.
In the case of positive charges, they repel other positive charges and attract negative charges. When a positive charge is present, it produces an electric field that extends outwards in all directions. Electric field lines emerge from positive charges and move away from them as they illustrate the direction of the force that a positive test charge would experience if placed nearby.
This behavior can be intuitively understood by considering the forces between charges. Like charges repel each other, pushing them apart. Therefore, if we bring a positive test charge close to a positive charge, it will experience a repulsive force and move away from it. This repulsive force is constantly present, and the electric field lines represent its direction and magnitude.
On the other hand, electric field lines from negative charges move towards them. Negative charges attract positive charges, which means that if a positive test charge is near a negative charge, it will experience an attractive force towards the negative charge. Consequently, the electric field lines point towards the negative charge, indicating the direction of this force.
In summary, the statement that all electric field lines start on positive charges makes sense because positive charges repel other positive charges. Thus, if a positive test charge were placed near a positive charge, it would experience a repulsive force, causing it to move away from the source charge. The electric field lines depict this behavior by starting from the positive charge and extending outwards.