Fundamentals of Electric Charge
Fundamentals of Electric Charge
Introduction
Electricity is one of the essential parts of our life and appliances like light, fan, mobile phone, television, calculator, computer and etc., need electricity for their operation. The rainbow comes in the blue sky due to electricity and most of the vehicle also wants it. The muscle contraction, nerve system, heartbeat, human thinking, and all chemical reaction requires electricity.
The flow of charge in a substance is called current or electricity. Atoms of similar structure bond together to create material and atom has both positive and negative charges. The atomic structure and electrical charge of atoms in the material will describe the property of the material and electric charge plays a vital role in all substances in the world.
Atomic Structure
All the particles in the universe are made up of atoms and it cannot be visualized with normal vision of human eyes. The nucleus (10-12 cm diameter) is a combination of neutron and protons and available at the center of the atom (10-8 cm diameter). It is positively charged because the protons and neutrons have positive and neutral/zero charges respectively. The electrons are negatively charged and they have 1836 times lower in mass when compared to proton(1.67262 × 10−27 kg) and electrons always orbiting in the region of the nucleus at a steady circular motion. The number of electrons in each orbit can be calculated using the formula 2n2, where n= orbit number from the nucleus
Figure 1. Atomic structure of Copper atom (courtesy: https://learn.sparkfun.com)
The number of electrons in the outermost orbit/shell or last orbit from nucleus determines the activity of each atom or the possibility to bond with nearby or other atom. It is called a valence shell and electrons available in this shell are called valence electrons.
The atom is said to be stable and less reactive when its last orbit is completely full as per the equation 2n2. Any substance or material can be identified using the structure of its atom. The atomic number is calculated based on the number of protons in an atom’s nucleus. Figure 1 shows the structure of a copper atom, it has an atomic number of 29 (29 protons in the nucleus) and the valence shell has 1 free electron.
Electric Charge
In some substance, electrons available in the valence shell are loosely bound (Copper has 1 loosely bond electron) with the nucleus and it has the tendency to flow from one to another atom. The free movement of electron is depending on the material. If electrons are able to move throughout the material from the valance shell, then the material is called conductor and the electrons held tightly in insulators.
Generally the atoms have neutral charge or atoms net electric charge is equal to zero or atoms are in the ground state, when the same number of electrons and protons are present with them. The charge of an atom can change when it gains or losses electrons. When an electron is added to an atom, it turns into a negatively charged or negative ion or anion. If an electron is removed from an atom, it becomes positively charged or positive ion or cation. The negatively or positively charged atom always creates an attractive or repulsive force and it is called an electric field. A positively charged atom will attract a negatively charged atom to make a bond and repel the same polarity atom and vice versa.
The electric charge is designated as q and its SI unit is Coulomb. The elementary charge e is the electric charge of an electron or proton.
Charge of one electron (-e) = -1.6 x10-19 Coulomb(C).
One proton charge (e) = 1.6 x10-19 Coulomb(C).
One negative Coulomb (-C) = 6.24 x1018 electrons
The movement of charge particles (electron or proton) in a specific period is called electric current (I). In most of the metals, the atoms can easily exchange electrons and its valence electrons tend to move anywhere and any direction within the material. The electrons will flow in a uniform direction, when a power source is connected to form a closed circuit and the electrons flow from negative terminal to positive terminal.
Charging a substance by induction:
When a positively charged substance is brought nearby a neural matter, the net charge of the substance creates an imbalance in the neutral matter. Due to the electric field, more free electrons in the neural matter will move towards one side where the positively charged substance is present by leaving the positive charges on the other side. If a wire is connected between ground and the neutral matter where the free electrons are accumulated, then the more number of accumulated electrons will reach the ground and it will make the neutral matter as positively charged one.
Property of charge
The charge is a scalar quantity and if there exists more than one charge, then they can be added directly to get net charge. The charge cannot be created or destroyed rather it can be transferred to one substance to another. The charge can be quantized and electric charge q = ne, where n is an integer and e = elementary charge of electron or proton. The same polarity charges ripple each other and opposite polarity charge attracts.
Conclusion
When the human hand is dragged across a towel, the surface contact between towel and hand will allow electrons to the human body thereby static charge is built on the skin. Instead of human skin and towel having zero charges, the charge inequality is created between them
After this, if the person touches any metal then, all the excess charges will move from the person to metal in order to restore the charge imbalance. In this case, the person may get an electric shock as the electrons leave suddenly from the skin to metal. Now the net electric charge will be zero. It can be understood that it not possible to create a net electric charge and it can change from one point to another.
The chemical bonding of atoms in a material is based on electrons in the outermost shell. The entire things in the universe are made up of atoms. If the atom is available, then there exist electric charges and it may be neutral, positive, or negative charges based on the material’s atomic structure. So, electric charge is also available in all parts of the universe and it can be carried by materials.