Undergraduate
  1. Classical mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. projectile motion  1.1.4. Relative speed  1.1.5. Uniform circular motion  1.1.6. Non-uniform circular motion  1.1.7. Reference frames and transformations  1.2. Newton's Laws of Motion  1.2.1. First law of motion  1.2.2. Second law of motion  1.2.3. Third Law of Motion  1.2.4. Applications of Newton's Laws  1.2.5. Friction and its types  1.2.6. Free Body Diagram  1.2.7. Constraints and pseudo-forces  1.3. Work and Energy  1.3.1. work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy in classical mechanics  1.3.5. Conservative and non-conservative forces  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.4. Speed and collisions  1.4.1. Linear momentum  1.4.2. Conservation of momentum  1.4.3. Impulse and impact force  1.4.4. Elastic and inelastic collision  1.4.5. Center of mass and speed  1.4.6. Rocket Propulsion  1.5. Rotational motion  1.5.1. Torque and Angular Momentum  1.5.2. Moment of inertia  1.5.3. Rotational Kinematics  1.5.4. Rotational Energy  1.5.5. Rolling Motion  1.5.6. Precession and gyroscopic motion  1.6. Gravitational force  1.6.1. Newton's law of universal gravitation  1.6.2. Gravitational potential energy  1.6.3. Orbital mechanics  1.6.4. Kepler's laws of planetary motion  1.6.5. Gravitational field and potential  1.7. Fluid mechanics  1.7.1. Pressure and Pascal's Principle  1.7.2. Buoyancy and Archimedes' principle  1.7.3. Fluid Dynamics and Bernoulli's Principle  1.7.4. Viscosity and Poiseuille's law  1.7.5. Surface tension and capillarity  1.8. Oscillations and waves  1.8.1. Simple Harmonic Motion  1.8.2. Damped and driven oscillations  1.8.3. Coupled oscillations and common modes  1.8.4. Wave properties and types  1.8.5. Sound Waves and the Doppler Effect  1.8.6. Wave interference and superposition
  2. Electromagnetism  2.1. Electrostatics  2.1.1. Electric charge and properties  2.1.2. Coulomb's law  2.1.3. Electric field and electric potential  2.1.4. Gauss's Law  2.1.5. Capacitance and Dielectric  2.1.6. Electric dipole and potential energy  2.2. Electric circuits  2.2.1. Current and Resistance  2.2.2. Ohm's law  2.2.3. Kirchhoff's Laws  2.2.4. RC Circuit  2.2.5. AC Circuits and Reactance  2.2.6. Electric power and energy  2.3. Magnetism  2.3.1. Magnetic Fields and Forces  2.3.2. Ampere's Law  2.3.3. Magnetic dipole moment  2.3.4. Biot-Savart law  2.3.5. Magnetic Materials and Hysteresis  2.4. Electromagnetic induction  2.4.1. Faraday's Law  2.4.2. Lenz's law  2.4.3. Self and mutual induction  2.4.4. Transformers and Inductive Circuits  2.5. Maxwell's equations  2.5.1. Gauss's law for electricity  2.5.2. Gauss's law for magnetism  2.5.3. Faraday's law of induction  2.5.4. Ampere-Maxwell law  2.5.5. Electromagnetic waves
  3. Thermodynamics  3.1. Laws of Thermodynamics  3.1.1. Zeroth law of thermodynamics  3.1.2. First law of thermodynamics  3.1.3. Second Law  3.1.4. Third Law  3.2. Heat and work  3.2.1. Heat transfer (conduction, convection, radiation)  3.2.2. Thermal expansion  3.2.3. Heat engines and refrigerators  3.2.4. Carnot cycle and efficiency  3.3. Statistical mechanics  3.3.1. Maxwell–Boltzmann distribution  3.3.2. Entropy and Probability  3.3.3. Partition function  3.3.4. Fermi–Dirac and Bose–Einstein statistics
  4. Optics  4.1. Geometrical Optics  4.1.1. Reflection and Refraction  4.1.2. Mirrors and lenses  4.1.3. Optical Instruments  4.1.4. Fermat's principle  4.2. Wave optics  4.2.1. Interference in wave optics  4.2.2. Diffraction  4.2.3. Polarization  4.2.4. Coherence and holography
  5. Quantum mechanics  5.1. Wave–particle duality  5.1.1. Blackbody radiation in wave–particle duality in quantum mechanics  5.1.2. Photoelectric effect  5.1.3. Compton scattering  5.1.4. De Broglie wavelength  5.2. Schrödinger Equation  5.2.1. Time-independent Schrödinger equation  5.2.2. Particle in a box  5.2.3. Quantum Tunneling  5.2.4. Potential wells and obstacles  5.3. Quantum States  5.3.1. Wave function  5.3.2. Quantum operators  5.3.3. Heisenberg uncertainty principle  5.3.4. Angular momentum and spin
  6. Relativity  6.1. Special relativity  6.1.1. Lorentz transformations  6.1.2. Time expansion and length contraction  6.1.3. Relativistic energy and momentum  6.2. General relativity  6.2.1. Principle of Equivalence  6.2.2. Schwarzschild metric  6.2.3. Gravitational waves  6.2.4. Black holes and event horizons
  7. Solid state physics  7.1. Crystal structure  7.1.1. Bravais lattices  7.1.2. X-ray diffraction  7.1.3. Band theory  7.1.4. Phonons and lattice vibrations  7.2. Electrical and Magnetic Properties  7.2.1. Conductors, Semiconductors and Insulators  7.2.2. Superconductivity  7.2.3. Hall effect
  8. Nuclear and particle physics  8.1. Atomic Structure  8.1.1. Atomic Model  8.1.2. Nuclear binding energy  8.2. Radioactivity  8.2.1. Alpha, beta, gamma decay  8.2.2. Half life  8.2.3. Nuclear Fission and Fusion  8.3. Particle physics  8.3.1. Standard Model  8.3.2. Quarks and Leptons  8.3.3. antimatter  8.3.4. Fundamental interactions
  9. Astrophysics and cosmology  9.1. Stellar evolution  9.1.1. Star formation  9.1.2. Black holes and neutron stars  9.1.3. White dwarfs and supernovae  9.2. Cosmology  9.2.1. The Big Bang Theory  9.2.2. Dark matter and dark energy  9.2.3. Cosmic microwave background

Undergraduate → Electromagnetism → Electrostatics ↓


Electric charge and properties


Electric charge is a fundamental property of matter. It's something that an object can have, like mass or volume, but it's not as easy to see. There are two types of electric charge: positive and negative. The most familiar objects that carry electric charge are protons and electrons. Protons have a positive charge, and electrons have a negative charge. Let's take a deeper look at the concept of electric charge and its properties.

What is electric charge?

Electric charge is a fundamental property that causes objects to experience a force when placed in an electromagnetic field. It is analogous to the concept of mass in the law of gravity. However, while mass is only one kind, charge is two kinds: positive and negative.

Types of fees

There are two types of fees:

  • Positive charge: This type of charge is carried by protons.
  • Negative charge: This charge is carried by electrons.

Objects with similar charges repel each other, while objects with opposite charges attract each other. This important property of charge is the basis of many electrical phenomena.

Basic properties of electric charge

Some of the fundamental properties of electric charge are as follows:

1. Quantization of charge

Quantization of charge means that charge exists in discrete quantities rather than in a continuous range. It is given by the equation:

q = n * e

Here, q is the charge, n is an integer (positive or negative), and e is the elementary charge (~1.6 × 10−19 coulombs).

2. Conservation of charge

Charge conservation is one of the fundamental properties of electric charge. It states that the total charge in an isolated system remains constant over time. This means that charge can neither be created nor destroyed, but it can be transferred from one part of the system to another.

3. Additive nature of charge

The total charge of a system is the algebraic sum of the individual charges. For example, if you have charges q1, q2, and q3, the total charge of the system is Q:

Q = q1 + q2 + q3 + ...

Electrostatic force and Coulomb's law

The force between two charges is described by Coulomb's law. It states that the force between two point charges q1 and q2 located at a distance r in a vacuum is proportional to the product of the charges and inversely proportional to the square of the distance between them:

F = k * (|q1 * q2| / r^2)

Where:

  • F is the magnitude of the force.
  • k is the Coulomb constant (~8.99 × 10 9 N m²/C²).
  • r is the distance between the centres of the two charges.

Visual example: electric field lines

Electric field lines provide a way to look at an electric field. They show the direction of the force exerted by the field on a positive charge and point away from positive charges and toward negative charges.

This diagram shows the field lines between a positive charge (in red) and a negative charge (in blue). The lines exit the positive charge and enter the negative charge, showing the direction of the electric field.

Electric fields and their properties

The electric field is the region around a charged particle where a force is applied on other charged particles. The strength of the electric field E created by a point charge q located at a distance r is given by:

E = k * (|q| / r^2)

The direction of the field is radially outward from the positive charge and radially inward towards the negative charge.

Characteristics of electric field lines

  • The lines start from the positive charge and end at the negative charge.
  • The number of lines is proportional to the magnitude of the charge.
  • The field is stronger where the lines are closer to each other.
  • Electric field lines never cross each other.

Electric potential energy

Like gravitational potential energy, charged objects also have electric potential energy. The potential energy U of a charge q in an electric field E is given by:

U = q * V

where V is the electric potential.

Applications of electric charge

The concept of electric charge is fundamental to many applications in physics and engineering:

  • Electronics: All electronic devices operate based on the manipulation and control of electrical charges.
  • Lightning: Lightning is the result of the build-up of electrical charge in clouds due to their interaction with air currents and the Earth's surface.
  • Capacitor: Capacitors store electrical energy by maintaining separation between positive and negative charges.

Conclusion

Electric charge is a fundamental aspect of nature, giving rise to electric forces and fields. Understanding electric charge and its properties is essential for exploring the broad field of electromagnetism and its many applications in technology and science. Future explorations include the integration of electric charge with other fundamental forces and the advancement of electrical technologies.


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Electric charge and properties

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