what is electric charge? Application & top 3 Properties

key point

• An atom is the smallest component or unit of any simple substance. It is the smallest recognized division of a chemical element.

• When two or more atoms combine a molecule is formed.
• Atomic weight is actually the ratio of the mass of the element to one-twelfth of the carbon atom.

• The atomic number in one molecule is equal to 6.022 × 1023 atoms.
• Element is the purest form of matter in which same kind of atoms are present like Ca, fe etc.

• Two or more elements combine in a definite proportion to form a new substance whose properties are completely different from the two elements are called compounds.
• The atomic weight of an element is a number that shows how much heavier an atom of the element is than (1/12th) of an atom of carbon-12. Or in other words how many times heavier it is than 1.008th of the mass of hydrogen.

• Atomic weight is approximately the sum of the number of protons and neutrons. Atomic number is equal to the number of protons or equivalent number of electrons present in the nucleus.
• The full form of “ISO” is “International Organization for Standardization”. Its headquarters is located in Geneva (Switzerland).

• The electron is the lightest particle of an atom. The weight of an electron is 1840 times less than the weight of a proton.
• Most of the atom is empty, only the nucleus is the dense part of the atom. The nucleus contains protons and neutrons, while electrons revolve in elliptical orbits.
• Neutron is present in the nucleus and does not move in any way. Neutron is a chargeless particle.

• When protons are brought near other protons, their potential energy will increase because work is done opposite to the repulsion force.

• In a liquid, the static charge always remains on the upper surface.

• In charging by induction, no charge of the charged body is spent, i.e. it is not lost. In this process, a charge of opposite nature is generated in a charged object without absorbing it.

Introduction-(WHAT IS CHARGE?)

• Electricity is an important source of energy nowadays.

• In present times, use of electrical energy is necessary to make every task of life simple and easy.

• Due to the increasing use of electrical energy in homes, educational institutions, various offices and industrial units, production of more electricity has become an important necessity at present.

• Due to rapid industrial development and various projects, skilled electricians will also be required in large numbers.

• The market for electricity and its related equipment is very vast and huge. Also, the innovations taking place in it every day are accelerating its development.

• Electricity is a physical phenomenon of the presence and flow of charges. Electricity cannot be seen or touched, it can only be felt by its effect.

What is electric Charge

• All objects present in nature experience the force of attraction or repulsion towards each other due to an imaginary property, this property is called charge.

• About 2500 years ago, Thales rubbed amber on silk, which attracted pieces. Small pieces of paper

• This effect was named electric.

• The word ‘electricity’ is derived from the Greek word electron meaning ‘amber’.

• There are mainly two types of electric charges – positive charge and negative charge. Information about these charges was given by Benjamin Franklin.

what is electricity

• Transfer of charges is the reason for generation of electricity.

• Electricity is classified into two parts based on the nature of motion of charges under it-

1. Static Electricity
2. Dynamic electrodynamics.

Static Electricity

• It exists in the form of electric charge and cannot be transferred from one place to another.

• If two substances are rubbed against each other, then due to exchange of mutual charges, they develop the property of attraction or repulsion.

• The branch of physics under which the properties of stationary charges and their related electric force, electric field, electric potential, electric capacitance and electric energy are studied is called static electricity.

Application of electric charge

Computer printers, paint sprayers and seismographs are also based on electrostatics.

Dynamic Electricity-

• Electricity produced by regular flow of charges is called dynamic electricity.

• Regular flow of charges takes place through the conductor.

• It can be transported from one place to another with the help of wires and cables.

• At present we can generate this type of energy from cells, batteries, dynamo, alternators.

Methods of electric Charge Generation-

Charges are generated mainly in three ways-

By friction-

• This experiment is used for static electricity.

• When two objects are rubbed together the transfer of charge takes place as per the table given below.

By conduction-

In this process, when two metallic objects are brought in contact with each other, charge is transferred between them. Like electric current in a circuit

By induction-

Through electromagnetic reactions, charge is transferred from one object to another without contact. For example, a transformer.

Properties of Electric Charge-

Additivity of charge-

• Charge is also a scalar quantity like mass.

• Algebraic addition is used to add different types of charges together.

Example: Suppose the charges present in a system are -2µC, +2µC and +4µC respectively. What is the total charge of the system?

Solution- We know that charge is a scalar quantity whose algebraic addition is possible.

Hence,

total charge (Q) = (-2µC) + (+2µC) + (+4µC) = +4µC

Charge Protection-

The total charge found in nature is always conserved. That is, charge can neither be created nor destroyed. It can only be transferred from one object to another.

Quantization of charge-

The charge of any object is an integer multiple of an elementary charge (e). Thus, the value of charge is Oe, 1e, -1e, 2e etc.

Therefore, the total charge on an object can be represented by the following formula-

Q=±ne

where : n = 0, 1, 2

e-1.6×10-19 C

Example: How many electrons or protons are present in one coulomb of charge?

Solution: We know

Q = ne

n = electron number -e-1.6 x 10-19C

n = 6.25 × 1018 electrons

Units of electric Charge-

• The SI unit of charge is coulomb.

• The CGS unit of charge is electrostatic unit (e.s.u.).

1 coulomb = 3×10° e.s.u.

1 e.s.u. = 3.33×10-10 coulomb

• Another unit of charge is faraday.

1 Faraday = 96500 Coulomb

• Charges are measured with an electroscope.

Coulomb’s Law-

This law was discovered by French scientist Charles Augustin de Coulomb.

This law is a quantitative statement about the force between two point charges.

This law was the basis for the development of the theory of electromagnetism.

If both the charges are of opposite sign then the force of attraction will exist between them. And if both the charges are of same sign then the force of repulsion will exist between them.

The value of electrostatic force between two point charges is proportional to the product of the two charges and inversely proportional to the square of the distance between them.

This law can be expressed in scalar or vector form. In scalar form, this law is as follows-

Limitations of Coulomb’s Law-

This law is true only for point charges.

This rule is not true for larger distances.

This law is not capable of calculating the distance between two charges less than 1.75 × 10-15 m (experimental). (Due to nuclear force)

Gauss’s Law-

This law establishes relation between the distribution of electric charges and the electric field generated due to them.

According to the rule, the electric flux emanating from a surface is (1\e) times the unit of electric charge surrounded by that surface. Where- e = permittivity of air or vacuum

Gauss’s law also explains Coulomb’s law. In differential form- VE = L where VE = electric field p = charge density

Conditions of Gauss’s Law –

This rule applies to point charges.

This law applies to infinite line charge.

This rule applies to an infinite sheet of charge.

This rule applies equally to spherical cells.

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