The Physics Hidden in an Umbrella: Electromagnetic Force
Context:
An ordinary automatic umbrella provides a simple illustration of several important concepts in physics, including elasticity, mechanical energy storage, atomic interactions and electromagnetic force.
| UPSC Relevance: GS-3 Science and Technology: Developments and their applications and effects in everyday life Prelims: Fundamental Forces, Standard Model of Physics |
How does an automatic umbrella open?
The main rod of an automatic umbrella contains a compressed spring and cylindrical sections.
- When we close an umbrella, the spring is compressed. This mechanical energy is stored as elastic potential energy.
- A locking mechanism or hook holds the spring in its compressed state.
- Pressing the button releases the lock. The spring expands and converts its stored elastic potential energy into mechanical energy, pushing the cylinders outward and unfolding the umbrella.
Thus, the button merely releases energy that was previously stored in the compressed spring.
How can a spring store Energy?
- When the spring is compressed: The atoms are forced closer together than their natural, stable equilibrium distance. The negatively charged electron clouds of neighbouring atoms begin to overlap and repel each other via the electromagnetic force.
- When the external force is removed (button is pushed in an umbrella), the material (springs) tends to return towards its equilibrium configuration, i.e, the similar charges push back to return to their original configuration. This is how the elastic force of any material arises.
The restoring force of an ordinary spring is an example of an electromagnetic force.
Four Fundamental Forces of Nature:
There are 4 fundamental forces of nature.
1. Gravitational Force: The force of attraction between objects that have mass. It is responsible for phenomena such as planetary motion and objects falling toward Earth. It is the weakest among the four fundamental forces.
2. Electromagnetic Force: The force of attraction or repulsion between electrically charged particles. Responsible for electricity, magnetism, chemical bonding and many macroscopic material properties.
3. Strong Nuclear Force: The strong nuclear force holds protons and neutrons together in a nucleus. It is the strongest among the four fundamental forces.
4. Weak Nuclear Force: Responsible for processes such as beta decay, and plays an important role in nuclear reactions such as those occurring in stars.
The Standard Model of Physics explains 3 of the 4 fundamental forces (electromagnetic, strong, and weak) but not gravity. The graviton, the force-carrying particle of gravity, has not been discovered yet.
UPSC PYQ 2013
Q. The known forces of nature can be divided into four classes, viz., gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?
(a) Gravity is the strongest of the four
(b) Electromagnetism acts only on particles with an electric charge
(c) Weak nuclear force causes radioactivity
(d) Strong nuclear force holds protons and neutrons inside the nucleus of an atom four
Answer: (a)