വൈദ്യുതകാന്തികത്വം: അടിസ്ഥാന ആശയങ്ങൾ

• Electromagnetism is a fundamental interaction of nature

Core Concepts

• Electromagnetism encompasses electric and magnetic fields and forces
• Electric fields are produced by electric charges
• Magnetic fields are produced by moving electric charges (electric current)
• Electromagnetic forces mediate interactions between charged particles

Electric Charge

• Electric charge is a fundamental property of matter
• It exists in discrete units that are multiples of the elementary charge (e ≈ 1.602 × 10⁻¹⁹ Coulombs)
• Charges can be positive or negative
• Like charges repel, opposite charges attract
• Charge is conserved in a closed system

Coulomb's Law

• Coulomb's Law quantifies the electrostatic force between two point charges
• The force is directly proportional to the product of the magnitudes of the charges
• The force is inversely proportional to the square of the distance between them
• F = k * |q1 * q2| / r², where F is the force, k is Coulomb's constant (approximately 8.9875 × 10⁹ N⋅m²/C²), q1 and q2 are the magnitudes of the charges, and r is the distance between them

Electric Field

• An electric field is a vector field that surrounds electric charges
• It exerts a force on other charges within the field
• The electric field (E) is defined as the force (F) per unit positive charge (q): E = F/q
• Electric field lines represent the direction and strength of the electric field
• The lines originate from positive charges and terminate on negative charges
• The density of field lines indicates the strength of the field

Electric Potential

• Electric potential (V) is the electric potential energy per unit charge
• It is a scalar quantity measured in volts (V)
• The electric potential difference between two points is the work done per unit charge to move a charge between those points
• V = W/q, where V is the electric potential difference, W is the work done, and q is the charge

Capacitance

• Capacitance (C) is a measure of a capacitor's ability to store electric charge
• A capacitor typically consists of two conductive plates separated by an insulator (dielectric)
• The capacitance is defined as the ratio of the charge (Q) stored on the capacitor to the voltage (V) across it: C = Q/V
• The unit of capacitance is the farad (F)

Electric Current

• Electric current (I) is the rate of flow of electric charge
• It is measured in amperes (A), where 1 A = 1 Coulomb/second
• Conventional current is defined as the flow of positive charge, even though in most materials, it is electrons (negative charge) that are moving

Resistance

• Resistance (R) is the opposition to the flow of electric current
• It is measured in ohms (Ω)
• Ohm's Law relates voltage (V), current (I), and resistance (R): V = IR

Electric Circuits

• An electric circuit is a closed loop that allows electric current to flow
• Circuits contain components such as resistors, capacitors, inductors, voltage sources, and current sources
• Resistors in series: R_total = R1 + R2 + R3 + ...
• Resistors in parallel: 1/R_total = 1/R1 + 1/R2 + 1/R3 + ...
• Kirchhoff's Laws are fundamental rules for analyzing electric circuits:
  • Kirchhoff's Current Law (KCL): The sum of currents entering a node equals the sum of currents leaving the node
  • Kirchhoff's Voltage Law (KVL): The sum of the voltage drops around a closed loop is zero

Magnetism

• Magnetism is a force caused by moving electric charges
• Magnets have north and south poles
• Like poles repel, opposite poles attract
• Magnetic fields are represented by magnetic field lines
• Field lines form closed loops, exiting from the north pole and entering the south pole

Magnetic Field

• A magnetic field (B) is a vector field that exerts a force on moving electric charges
• The force on a charge q moving with velocity v in a magnetic field B is given by the Lorentz force: F = q(v × B)
• The direction of the force is perpendicular to both the velocity and the magnetic field (right-hand rule)
• The unit of magnetic field is the tesla (T)
• 1 Tesla = 1 N/(A⋅m)

Sources of Magnetic Fields

• Moving electric charges (currents) create magnetic fields
• A current-carrying wire produces a magnetic field around it
• The magnetic field due to a long, straight wire is proportional to the current and inversely proportional to the distance from the wire
• A solenoid (coil of wire) produces a relatively uniform magnetic field inside the coil

Magnetic Materials

• Materials can be classified based on their magnetic properties:
  • Ferromagnetic materials (e.g., iron, nickel, cobalt): Strongly attracted to magnetic fields and can be permanently magnetized
  • Paramagnetic materials (e.g., aluminum, platinum): Weakly attracted to magnetic fields
  • Diamagnetic materials (e.g., copper, gold, water): Weakly repelled by magnetic fields

Electromagnetic Induction

• A changing magnetic field induces an electromotive force (EMF) or voltage in a conductor
• This phenomenon is known as electromagnetic induction
• Faraday's Law of Induction: The induced EMF in a closed loop is equal to the negative rate of change of magnetic flux through the loop: EMF = -dΦ/dt, where Φ is the magnetic flux

Magnetic Flux

• Magnetic flux (Φ) is a measure of the amount of magnetic field lines passing through a given area
• It is defined as Φ = B⋅A = BAcosθ, where B is the magnetic field strength, A is the area, and θ is the angle between the magnetic field and the normal to the area
• The unit of magnetic flux is the weber (Wb)

Lenz's Law

• Lenz's Law states that the direction of the induced EMF is such that it opposes the change in magnetic flux that produced it
• This means the induced current creates a magnetic field that opposes the original change in magnetic field

Inductance

• Inductance (L) is a measure of a coil's ability to induce an EMF in itself or in a nearby circuit due to a changing current
• It is defined as the ratio of the magnetic flux linkage to the current: L = NΦ/I, where N is the number of turns in the coil, Φ is the magnetic flux, and I is the current
• The unit of inductance is the henry (H)

Electromagnetic Waves

• Electromagnetic waves are disturbances in electric and magnetic fields that propagate through space
• They are produced by accelerating electric charges
• Electromagnetic waves are transverse waves, meaning the electric and magnetic fields are perpendicular to each other and to the direction of propagation
• Electromagnetic waves travel at the speed of light (c ≈ 3.0 × 10⁸ m/s) in a vacuum

Properties of Electromagnetic Waves

• Electromagnetic waves carry energy and momentum
• They exhibit wave phenomena such as reflection, refraction, diffraction, and interference
• Electromagnetic waves have a wide range of frequencies and wavelengths, forming the electromagnetic spectrum
• The electromagnetic spectrum includes (from lowest to highest frequency): radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays
• The energy of an electromagnetic wave is related to its frequency by E = hf, where h is Planck's constant (approximately 6.626 × 10⁻³⁴ J⋅s)

Applications of Electromagnetism

• Electromagnetism has numerous applications in various fields:
  • Electric motors and generators
  • Transformers
  • Radio and television communication
  • Medical imaging (MRI, X-rays)
  • Electronics and computers
  • Lighting and heating