Understanding Electromagnetism

• Electromagnetism is one of the four fundamental forces of nature, encompassing electric and magnetic phenomena.

Core Concepts

• Electric charge is a fundamental property of matter, with positive and negative types.
• Like charges repel, and opposite charges attract.
• The SI unit of electric charge is the coulomb (C).
• Electric current is the rate of flow of electric charge, measured in amperes (A).
• Voltage (electric potential difference) is the electric potential energy difference per unit charge, measured in volts (V).
• Resistance is the opposition to the flow of electric current, measured in ohms (Ω).
• Magnetism is a force caused by the motion of electric charges.
• Magnetic fields are created by moving electric charges and magnetic materials.
• Magnetic fields exert forces on moving electric charges and magnetic materials.
• Electromagnetism describes the interaction of electric and magnetic fields.
• Electromagnetic waves are disturbances in electric and magnetic fields that propagate through space.

Electric Fields

• An electric field is a region of space around an electric charge where a force would be exerted on other electric charges.
• Electric field lines represent the direction and strength of the electric field.
• Electric field lines originate from positive charges and terminate on negative charges.
• The electric field strength (E) is defined as the force per unit charge, measured in newtons per coulomb (N/C).
• The electric field due to a point charge is given by Coulomb's law: E = kQ/r², where k is Coulomb's constant, Q is the charge, and r is the distance from the charge.
• Electric potential (V) is the electric potential energy per unit charge, 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.
• Equipotential surfaces are surfaces where the electric potential is constant.
• Electric fields are always perpendicular to equipotential surfaces.

Magnetic Fields

• A magnetic field is a region of space around a magnet or moving electric charge where a magnetic force is exerted.
• Magnetic field lines represent the direction and strength of the magnetic field.
• Magnetic field lines form closed loops; they do not begin or end at a point.
• The magnetic field strength (B) is measured in teslas (T).
• The magnetic force on a moving charge is given by F = qvBsinθ, where q is the charge, v is the velocity, B is the magnetic field strength, and θ is the angle between the velocity and the magnetic field.
• The direction of the magnetic force is perpendicular to both the velocity and the magnetic field (right-hand rule).
• A current-carrying wire produces a magnetic field around it.
• The magnetic field due to a long, straight wire is given by B = μ₀I/(2πr), where μ₀ is the permeability of free space, I is the current, and r is the distance from the wire.
• Solenoids and toroids are used to create uniform magnetic fields.

Electromagnetism

• Electromagnetism combines electric and magnetic forces into a single fundamental force.
• Faraday's law of induction states that a changing magnetic field induces an electromotive force (EMF) in a circuit.
• The induced EMF is proportional to the rate of change of magnetic flux: EMF = -N(dΦ/dt), where N is the number of turns in the circuit and Φ is the magnetic flux.
• Lenz's law states that the direction of the induced current is such that it opposes the change in magnetic flux that produced it.
• Maxwell's equations are a set of four equations that describe the behavior of electric and magnetic fields.
• Maxwell's equations predict the existence of electromagnetic waves that propagate at the speed of light.
• Electromagnetic waves are transverse waves consisting of oscillating electric and magnetic fields perpendicular to each other and to the direction of propagation.

Electromagnetic Spectrum

• The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.
• From lowest to highest frequency (longest to shortest wavelength), the electromagnetic spectrum includes: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.
• Radio waves are used for communication, broadcasting, and radar.
• Microwaves are used for cooking, communication, and radar.
• Infrared radiation is associated with heat.
• Visible light is the portion of the electromagnetic spectrum that is visible to the human eye.
• Ultraviolet radiation can cause sunburn and skin cancer.
• X-rays are used for medical imaging.
• Gamma rays are emitted by radioactive materials and are used in cancer treatment.

Circuits

• An electric circuit is a closed loop that allows electric current to flow.
• A series circuit is a circuit in which components are connected end-to-end, so the same current flows through each component.
• In a series circuit, the total resistance is the sum of the individual resistances: R_total = R1 + R2 + R3 + ...
• A parallel circuit is a circuit in which components are connected side-by-side, providing multiple paths for the current to flow.
• In a parallel circuit, the reciprocal of the total resistance is the sum of the reciprocals of the individual resistances: 1/R_total = 1/R1 + 1/R2 + 1/R3 + ...
• Ohm's law states that the voltage across a resistor is proportional to the current flowing through it: V = IR.
• Electric power is the rate at which electrical energy is converted into other forms of energy, measured in watts (W).
• Electric power is given by P = VI = I²R = V²/R.
• Capacitors store electrical energy in an electric field, measured in farads (F).
• Inductors store energy in a magnetic field, measured in henries (H).
• Alternating current (AC) is an electric current that periodically reverses direction.
• Direct current (DC) is an electric current that flows in one direction only.
• Transformers are used to increase or decrease the voltage of an AC power supply.