Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Electricity and Magnetism ↓


Electrostatics


Electrostatics is the branch of physics that deals with the study of forces, fields, and potentials produced by stationary electric charges. It is one of the fundamental areas of electricity and magnetism. This subject focuses on electrical phenomena that occur at rest, meaning that the charges do not move but instead create electric fields that affect their surroundings.

Basic concepts of electrostatics

Electric charge

Electric charge is a fundamental property of matter that exerts a force on matter when placed in an electromagnetic field. There are two types of charges: positive and negative. Like charges repel each other, while unlike charges attract each other. This is called the law of charges.

Atoms and charge

At the atomic level, protons have a positive charge, electrons have a negative charge, and neutrons are neutral, meaning they have no charge. The unit of electric charge is the coulomb, represented by C

Conductors and insulators

Substances can be classified based on how freely charges can move around in them. Conductors, such as metals, allow charges to move around freely because of the presence of free electrons. Insulators, such as rubber or glass, do not allow charges to move around freely because they lack free electrons.

Coulomb's law

Coulomb's law states the amount of force between two stationary, electrically charged particles. According to Coulomb's law, the force (F) between two charges (q_1 and q_2) is proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance (r) between them. It is expressed mathematically as:

F = k * (|q_1 * q_2|) / r^2

Where:

  • F is the force between the charges in newtons.
  • k is the Coulomb constant, approximately 8.988 × 10^9 N m^2/C^2.
  • |q_1 * q_2| is the product of the absolute values of the charges.
  • r is the distance between the centres of the two charges.

Example

Consider two charges, q_1 = 3 μC and q_2 = -2 μC, placed at a distance of 0.5 m from each other. The force between them will be calculated as follows:

F = 8.988 × 10^9 N m^2/C^2 * ((3 × 10^-6 C) * (-2 × 10^-6 C)) / (0.5 m)^2

Electric field

The electric field is the region around a charged particle where a force will be experienced by other charges. The strength of this field is referred to as the electric field intensity or electric field strength, denoted by E The electric field produced by a charge q at a distance r is given as:

E = k * |q| / r^2

The direction of the electric field is the direction that a positive test charge will move if placed within the field. Electric fields are vector fields, which means they have both magnitude and direction.

Visual example

+Q

In this diagram, the blue lines show the direction of the electric field emanating from the positive charge.

Electric field lines

Electric field lines are graphical representations to show the direction of the electric field. The main properties of these lines are as follows:

  • They emerge from the positive charge and terminate at the negative charge.
  • The density of the field lines indicates the strength of the field: closer lines mean a stronger field.
  • Field lines never cross each other.

Electric potential and potential difference

Electric potential at a point in a field is the work done to move a unit positive charge from infinity to that point. It is measured in volts (V). Potential difference between two points is the work done to move a unit charge from one point to another.

V = W / q

Where:

  • V is the electric potential.
  • W is the work done in joules.
  • q is the charge in coulombs.

Capacitors and capacitors

Capacitance is the ability of a system to store electric charge. A capacitor is an electrical component used to store energy electrostatically in an electric field. The capacitance C is given by:

C = Q / V

Where Q is the stored charge, and V is the potential difference across the capacitor.

Parallel plate capacitor

A standard example of a capacitor is the parallel plate capacitor, which has two conducting plates separated by an insulating material. The capacitance of a parallel plate capacitor is given by:

C = ε₀ * A / d

Where:

  • ε₀ is the permittivity of free space.
  • A is the area of a plate.
  • d is the separation between the plates.

Applications of electrostatics

Electrostatics is important in many applications and technologies, including:

  • Electrostatic precipitators: Used to remove fine particles such as dust and smoke from flowing gases in industrial processes.
  • Photocopiers: use electrostatic charges to transfer ink or toner to paper.
  • Capacitors in electronics: Essential components in electronic circuits for electric storage and regulation.

Example calculation

Example 1: Calculate the force between two charges of 5μC and -3μC that are 2 m apart:

F = 8.988 × 10^9 N m^2/C^2 * ((5 × 10^-6 C) * (-3 × 10^-6 C)) / (2 m)^2

Example 2: Determine the electric field at a point located 0.3 m away from an 8μC charge:

E = 8.988 × 10^9 N m^2/C^2 * (8 × 10^-6 C) / (0.3 m)^2

Simulation

Theoretical calculations and visual examples help to understand electrostatics, while simulations allow testing concepts in a virtual environment. Several online platforms provide interactive simulations to explore and visualize the behavior of charges and electric fields.

Closing thoughts

Electrostatics is an essential foundation of electricity and magnetism, providing information about the behavior of charges in a static state. Understanding electrostatics is the basis for advances in technology and science, enabling the development of countless innovations and devices that take advantage of electrical properties for a variety of applications.


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Electrostatics

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