Nuclear Force: Definition, Characteristics and Potential Energy Curve

Learn about Nuclear Force, its characteristics, short-range nature, charge independence, and potential energy curve with easy Class 12 Physics notes

Defination: Nuclear Force 

Nuclear force is the force that binds protons and neutrons (collectively called nucleons) inside the nucleus. Since positively charged protons repel each other due to the Coulomb force, a much stronger attractive force is required to hold the nucleus together. This force is known as the nuclear force.

The binding energy per nucleon for medium-mass nuclei is approximately 8 MeV, which is much larger than the binding energy found in atoms. This indicates that nuclear force is extremely strong and plays a crucial role in maintaining nuclear stability.

Characteristics of Nuclear Force

1. Nuclear Force is Very Strong

Nuclear force is much stronger than both the Coulomb force and the gravitational force. It is strong enough to overcome the electrostatic repulsion between protons and keep nucleons bound within the nucleus.

2. Nuclear Force is a Short-Range Force

The nuclear force acts only over a very short distance, typically a few femtometres (fm). Beyond this range, its effect rapidly decreases and becomes negligible.

3. Potential Energy Curve of Nuclear Force

The potential energy between two nucleons varies with their separation distance.

• The potential energy reaches a minimum at approximately 0.8 fm.
• For distances greater than 0.8 fm, the nuclear force is attractive.
• For distances less than 0.8 fm, the nuclear force becomes strongly repulsive.
• This repulsive nature at very small distances prevents nucleons from collapsing into each other.

4. Charge Independence of Nuclear Force

The nuclear force between proton-proton (p-p), neutron-neutron (n-n), and proton-neutron (p-n) pairs is approximately the same. Therefore, nuclear force does not depend on electric charge.

5. No Simple Mathematical Formula

Unlike Coulomb's law and Newton's law of gravitation, there is no simple mathematical expression that completely describes the nuclear force.

Key Points of Nuclear Force

• Nuclear force binds nucleons inside the nucleus.
• It is much stronger than Coulomb and gravitational forces.
• It is a short-range force.
• It is charge-independent.
• It is attractive for distances greater than 0.8 fm.
• It is strongly repulsive for distances less than 0.8 fm.

Conclusion

Nuclear force is one of the fundamental forces of nature responsible for holding the atomic nucleus together. Its strong, short-range, and charge-independent nature ensures the stability of nuclei despite the electrostatic repulsion between protons.

Frequently Asked Questions (FAQs)

Q1. What is nuclear force?

Nuclear force is the strong attractive force that binds protons and neutrons together inside the atomic nucleus.

Q2. Why is nuclear force required in the nucleus?

Nuclear force is required to overcome the electrostatic repulsion between positively charged protons and keep the nucleus stable.

Q3. Is nuclear force stronger than Coulomb force?

Yes, nuclear force is much stronger than the Coulomb force at short distances inside the nucleus.

Q4. What is the range of nuclear force?

Nuclear force acts over a very short distance of a few femtometres (fm).

Q5. At what distance is the potential energy minimum between two nucleons?

The potential energy is minimum at approximately 0.8 fm.

Q6. When is nuclear force attractive?

Nuclear force is attractive when the separation between nucleons is greater than 0.8 fm.

Q7. When does nuclear force become repulsive?

Nuclear force becomes strongly repulsive when the separation between nucleons is less than 0.8 fm.

Q8. Does nuclear force depend on electric charge?

No. Nuclear force is nearly the same between proton-proton, neutron-neutron, and proton-neutron pairs.

Q9. Why is nuclear force called a short-range force?

It is called a short-range force because its effect rapidly decreases and becomes negligible beyond a few femtometres.

Q10. Is there a simple formula for nuclear force?

No. Unlike gravitational and electrostatic forces, there is no simple mathematical formula for nuclear force.