Short Answer
Like charges repel because their electric fields push against each other, creating a force that drives them apart. Positive–positive or negative–negative charges produce similar electric field patterns, and this similarity causes repulsion.
Unlike charges attract because their electric fields pull toward each other. A positive charge and a negative charge create opposite field directions, and this difference causes an attractive force between them. This attraction or repulsion happens even without direct contact.
Detailed Explanation
Why like charges repel and unlike charges attract
The behavior of electric charges—repulsion between like charges and attraction between unlike charges—is a fundamental rule in electrostatics. This behavior helps explain how objects interact, how electric fields form, and how forces act at a distance. To understand why this happens, we must look at electric fields, electric forces, and the nature of charged particles.
Electric charges create electric fields around them. These fields extend in all directions and influence any other charge brought nearby. The interaction between electric fields is what creates the electric force. The direction of these fields is important:
- A positive charge produces an outward field.
- A negative charge produces an inward field.
The way these fields combine determines whether the force is attractive or repulsive.
Repulsion between like charges
When two like charges—both positive or both negative—are brought close, their electric fields point in opposite directions where the charges face each other. For example, two positive charges produce field lines that go outward from each charge. When these outward fields meet, they push against each other.
This pushing effect creates electric repulsion. The field lines never meet but bend away from each other, showing that the charges try to move apart. Because the force acts along the line joining the charges, both charges experience a force that drives them away from each other.
This happens because nature does not allow two similar electric field directions to overlap smoothly. The electric energy increases when like charges come near each other, so the system tries to reduce this energy by pushing the charges apart.
Attraction between unlike charges
Unlike charges—one positive and one negative—produce electric fields that complement each other. A positive charge sends field lines outward, while a negative charge pulls them inward. When these two charges are near, the field lines naturally connect from the positive charge to the negative charge.
This connection creates a smooth and stable electric field pattern. The energy of this arrangement is lower, so the system tries to pull the two charges together to maintain this stable state. This results in electric attraction.
Because field lines flow from positive to negative, a positive charge feels a pull toward the negative charge, and the negative charge feels a pull toward the positive charge. Both charges experience forces bringing them closer.
Role of Coulomb’s law
Coulomb’s law mathematically explains the force between charges. It states that:
- The strength of the force depends on the magnitudes of the charges.
- The force decreases with distance.
- The force is repulsive for like charges and attractive for unlike charges.
Coulomb’s law supports what we observe in electric fields. The direction of the force is determined by the nature of the charges:
- Positive–positive → repulsion
- Negative–negative → repulsion
- Positive–negative → attraction
This rule applies to all point charges in nature, from electrons and protons to charged objects around us.
Energy and stability
The attraction and repulsion of charges can also be understood in terms of energy.
- When like charges are brought close, the electric potential energy increases, making the system unstable. The system reduces this energy by moving the charges apart.
- When unlike charges come close, the electric potential energy decreases, making the system stable. The system naturally moves the charges closer to lower its energy.
This behavior shows that unlike charges attract because nature favors stable, low-energy arrangements.
Examples in daily life
- A comb rubbed on hair attracts paper bits because the charged comb attracts opposite charges in the paper.
- Two charged balloons repel each other because both balloons gain the same type of charge.
- In atoms, electrons are attracted to the proton in the nucleus because they carry opposite charges.
These examples show the universal behavior of charges in real situations.
Conclusion
Like charges repel because their electric fields push against each other, creating a repulsive force. Unlike charges attract because their electric fields flow smoothly from positive to negative, forming a stable arrangement. This attraction and repulsion follow Coulomb’s law and are essential for understanding electric forces, atomic structure, and many natural phenomena.