class: 9 unit:1:Introduction to Electrostatics

Electricity:

  • Electricity is a fundamental aspect of modern life, powering our homes, businesses, industries, and technology. It’s a form of energy resulting from the movement of charged particles, typically electrons, through a conductor. Understanding the basics of electricity is important to understanding how various electrical systems work and how to use them safely and effectively.

Key Concepts:

Atoms and Charges: Atoms, the building blocks of matter, consist of protons (positively charged), neutrons (no charge), and electrons (negatively charged). An electric charge is created when electrons move from one atom to another. Materials can be classified as conductors, insulators, or semiconductors based on their ability to conduct electricity.

Voltage, Current, and Resistance:

Voltage (V)

  •  Voltage is the force or “push” that drives electric charges to move through a circuit. It’s measured in volts and symbolized by “V”.

Current (I):

  • Current is the flow of electric charge through a conductor. It’s measured in amperes (amps) and symbolized by “I”.

Resistance (R):

  • Resistance opposes the flow of electric current. It’s measured in ohms (Ω) and symbolized by “R”.

Ohm’s Law:

  • The voltage across a conductor is directly proportional to the current passing through it, given that the temperature remains constant
  • Ohm’s Law describes the relationship between voltage, current, and resistance in an electrical circuit:

V= IR…………………(I)

Where:

  • V is the voltage across the circuit (in volts).
  • I is the current flowing through the circuit (in amperes).
  • R is the resistance of the circuit (in ohms).

Electric Circuits:

  • An electric circuit is a closed loop through which electric current can flow. Circuits can be classified into two types:

Series Circuit:

  • Components are connected end-to-end, forming a single path for current flow.

Parallel Circuit:

  • Components are connected across common points, providing multiple paths for current flow.

Power:

  • Power is the rate at which electrical energy is transferred by an electric circuit. It’s measured in watts (W) and can be calculated using the formula:

Power = v*I …………………..(2)

Classification of electricity

Statics Electricity:

Static electricity occurs when there’s an imbalance of positive and negative charges on an object.

  • This imbalance can happen through various means, such as friction, induction, or conduction.

  • When these charges build up on an object, they can create a static electric field, which can cause effects like attraction or repulsion between objects, as well as phenomena like sparks or electric shocks.

Example: One simple example of static electricity is when you rub a balloon against your hair. When you do this, electrons from your hair are transferred to the surface of the balloon, leaving your hair with a positive charge and the balloon with a negative charge. Because opposite charges attract, the balloon will then stick to your hair or to a wall for a while due to the static electric force between the charged objects. This is a common demonstration of static electricity in action.

Dynamic Electricity:

  • Dynamic electricity can be defined as the flow of electric charge through a conductor, typically in the form of an electric current.
  • This flow of charge can occur in various forms, including direct current (DC) and alternating current (AC).
  • In DC, the electric charge flows consistently in one direction, while in AC, the direction of the charge alternates periodically.
  • Dynamic electricity powers much of modern technology and infrastructure, including electrical appliances, lighting systems, motors, and electronics. It is the basis for electrical circuits and is governed by principles described by Ohm’s law and other electrical laws and theories.

Applications and uses of electricity :

Electricity has become an integral part of modern life, powering numerous devices, systems, and industries. Here are some key applications and uses of electricity:

  1. Lighting: Electricity powers various lighting systems, including bulbs, fluorescent tubes, LEDs, and more, illuminating homes, offices, streets, and public spaces.
  2. Heating and Cooling: Electricity is used for heating and cooling purposes in residential, commercial, and industrial settings. It powers electric heaters, air conditioners, heat pumps, and electric radiators.
  3. Transportation: Electric vehicles (EVs) utilize electricity to power their motors, enabling eco-friendly transportation options for individuals and reducing reliance on fossil fuels.
  4. Communication: Electricity powers communication technologies such as telephones, computers, smartphones, and the Internet, facilitating global connectivity and information exchange.
  5. Entertainment: Electricity is essential for various forms of entertainment, including televisions, radios, gaming consoles, and audio systems, providing recreational options for individuals and families.
  6. Manufacturing: Electricity is a primary energy source in manufacturing industries, powering machinery, equipment, and processes for producing goods across sectors such as automotive, electronics, textiles, and more.
  7. Medical Applications: Electricity is used in various medical devices and equipment, including MRI machines, X-ray machines, defibrillators, and electrocardiographs, supporting healthcare diagnostics and treatments.
  8. Cooking: Electric stoves, ovens, microwaves, and other kitchen appliances rely on electricity for cooking and food preparation, offering convenience and precision in culinary tasks.
  9. Renewable Energy Generation: Electricity generated from renewable sources such as solar, wind, hydro, and geothermal power plays a crucial role in sustainable energy production, mitigating environmental impacts associated with fossil fuels.
  10. Security Systems: Electricity powers security systems such as alarms, surveillance cameras, and access control systems, enhancing safety and protection for homes, businesses, and public spaces.
  11. Research and Development: Electricity is vital for conducting experiments, powering laboratory equipment, and running scientific simulations, supporting advancements in various fields including physics, chemistry, biology, and engineering.
  12. Agriculture: Electricity is used in agricultural operations for tasks such as irrigation, ventilation, lighting in greenhouses, and operating machinery like tractors and harvesters, contributing to increased efficiency and productivity in farming practices.

Atom:

  • An atom is the basic unit of matter and the smallest particle of an element that retains its properties. Atoms are made up of three types of subatomic particles: protons, neutrons, and electrons.
  • An atom is the smallest unit of an element that retains the chemical properties of that element
  • Atoms are composed of three subatomic particles: protons, neutrons, and electrons. Protons and neutrons are found in the nucleus at the center of the atom, while electrons orbit the nucleus in electron shells or energy levels.

Proton :

  • Protons are positively charged particles located in the nucleus (center) of the atom. it is denoted by (p+)

Neutron:

  • Neutrons are neutrally charged particles also located in the nucleus. Neutral means no charge.
  • Neutrons has no charge.

Electrons:

  • Electrons are negatively charged particles that orbit around the nucleus. it is denoted by (e–)
  • The charge on an electron is  1.6×10-16 c.

Atom

Atomic weight:

  • The total weight of an atom is known as atomic weight. In other words, an atomic weight can be defined as the average weight of an element with respect to all its isotopes and their relative abundance.
  • Atomic weight is measured in AMU or Dalton.

Atomic Number:

  • The atomic number can be defined as the total number of protons present in the uncles of an atom is called the atomic number.
  • The total number of protons and neutrons present in the nucleus of an atom is called the mass number.

Electric charge:

    • Electric charge can be defined as the amount of charge transformed from one body to another body by different models like conductors, induction, and specific methods.
    • Electric charge can be categorized as two types and these are positive electric charge and negative charge.
    • The SI unit of electric charge is coulomb  C.

Coulomb’s law:

  • Coulomb’s law states that the force of attraction or repulsion between two charges is directly proportional to the product of charges and inversely proportional to the square distance between the charges.
  • Let us consider two charges having magnitude Q1 and Q2, Which are separated by a distance of d meters as shown below in diagrams

Coulomb's law

  • Mathematically coulomb’s law can be expressed as.

                         F ∝ Q1 *Q2 …………………………(1)

   F ∝ 1/d2  …………………………..(2)

  • Now combining equation 1 and 2, We have

F = k Q1  * Q2 / d2 …………………..(3)

Where:

  • is the electrostatic force between the charges,
  • is Coulomb’s constant (8.9875×109 N m2/C2),
  • Q1 and Q are the magnitudes of the charges,
  • d is the distance between the charges.

Equation 3 is known as Coulomb’s law in mathematical form.

Numerical 1: Two point charges, 𝑞1=+3 μ, and 𝑞2=−5 μ are placed 10 cm apart in the air. Calculate the force between them.

solution.

  • 𝑞1=+3 μC
  • 𝑞2=−5 μC
  • d=10 cm=0.1 m
  • k = 9 x 109 Nm2C−2

  Using Coulomb’s Law:

F = k Q1  * Q2 / d2   where is Coulomb’s constant (9×109N m2/C2).Substituting values:

F = (9 × 109 ) [(3x 10-6 ) × (5 x 10-6) / (0.1)2]

F=   – 13.5N
Numerical 2:Two-point charges, q1 = +9 μC and q2 = 4 μC are separated by a distance d = 12 cm. What is the magnitude of the electric force?

Solution:

  • k = 9 x 109 Nm2C−2
  • q1 = +9μC = 9 × 10-6 C
  • q2 = +4μC = 4 × 10-6C
  • d = 12cm = 0.12m

We know that,

F = k (q1q2 ∕ d2)

F = (9 × 109 ) [(9x 10-6 ) × (4 x 10-6) / (0.12)2]

F = (9 × 109 ) [36 × 10-12 /0.0144]

F = 22.5N

The electric force between the charges is approximately 22.5 N.

Numerical 3:Two point charges, 𝑞1=4 µC, and 𝑞2=−6 µC are placed 10 cm apart in the air. Calculate the magnitude of the electrostatic force between them.

Solution: Given:

  • Charge 𝑞1=4 µC
  • Charge 𝑞2=−6 µC
  • Distance 𝑟=10 cm=0.1 m
  • k= (9×109 N m2/C2)

We know that

            F = k (q1q2 ∕ d2)

             F= (9 × 109 ) [(4x 10-6 ) × (-6 x 10-6) / (0.1)2]

               F = -21.6N.

 All numerals are solved by Er. Basant Kumar yadav

Electric Field:

 An electric field is a region around a charged particle or object. Charged particles exert attractive forces on each other when their charges are opposite, and repulse each other when their charges are the same.

The formula of the electric field is given as,

E = F /Q

Where,

  • E is the electric field.
  • F is the force.
  • Q is the charge.

Electric Potential:

An electric potential is the amount of work energy needed per unit of electric charge to move the charge from one place to another in an electric field.

An electric potential is also called an electric field or electrostatics potential and is measured in volts.

Electric Potential Difference

An electric potential is the work done per unit charge to move a unit charge from one point to another in an electric field.

Electric potential difference is also known as voltage, and electric potential difference is usually known as voltage difference, and its SI unit is volt.

Electric Energy:

Electric energy is the energy generated by the movement of electrons from one point to another.

Generally, electrical energy is referred to as the energy that has been converted from electric potential energy. Electric potential energy is measured in joules or watt-hours.

Sources of Electrical Energy:

The prime sources of electrical energy include renewable sources renewable sources like solar and wind, and nonrenewable sources like fossil energy fuels and nuclear power.

Hydropower: 

Hydropower is the main source of electrical energy in Nepal. Electrical energy is created from water stored in huge dams. The energy created by the water released from these dams is transformed into electricity by hydroelectric turbines and generators

 

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