Electromagnetism

Understanding electricity, magnetism, and electromagnetic waves

Subcategories

Electric Current & Circuits

Understanding electric current, resistance, and how circuits work

Electromagnetic Waves

Understanding electromagnetic radiation, the spectrum, and wave applications

Electrostatics

Understanding static electricity, electric fields, and electric potential

Magnetism

Understanding magnetic fields, magnetic forces, and electromagnetic induction

Topics

Batteries work by converting chemical energy into electrical energy through chemical reactions. They contain two electrodes (anode and cathode) separated by an electrolyte, with chemical reactions creating voltage that drives current through circuits.

How do circuits work?

Circuits work by providing a complete path for electric current to flow from a voltage source through components and back. Current flows when the circuit is closed, powering devices and allowing electricity to do work.

How do series and parallel circuits differ?

In series circuits, components are connected end-to-end so current flows through each component sequentially. In parallel circuits, components are connected across the same voltage source so current splits among branches. Series circuits have the same current everywhere but voltage divides; parallel circuits have the same voltage but current divides.

How do transformers work?

Transformers work using electromagnetic induction—alternating current in the primary coil creates a changing magnetic field, which induces voltage in the secondary coil. The voltage ratio equals the turns ratio, allowing transformers to increase or decrease voltage while maintaining the same frequency.

What is alternating current?

Alternating current (AC) is electric current that periodically reverses direction, flowing back and forth in a circuit. Unlike direct current (DC) which flows in one direction, AC current changes direction many times per second, typically 50 or 60 times per second (hertz) in power systems.

What is electric current?

Electric current is the flow of electric charge, typically electrons moving through a conductor. It's measured in amperes (amps) and represents the rate at which charge flows through a circuit.

What is electrical energy?

Electrical energy is the energy associated with electric charges and their movement. It's the energy transferred when electric current flows through a circuit, calculated as energy = power × time or energy = voltage × charge. Electrical energy can be converted to other forms like light, heat, or mechanical work.

What is Ohm's law?

Ohm's law states that voltage equals current times resistance (V = I × R). It describes the relationship between voltage, current, and resistance in electrical circuits, showing how these quantities relate.

What is power in electricity?

Electrical power is the rate at which electrical energy is transferred or consumed. It's measured in watts and calculated as power = voltage × current (P = V × I). Power represents how fast energy is used or produced in an electrical circuit.

What is resistance?

Resistance is a material's opposition to electric current flow. It's measured in ohms and determines how much current flows for a given voltage. Higher resistance means less current flows.

How does Bluetooth work?

Bluetooth works by transmitting data using short-range radio waves in the 2.4 GHz frequency band. Devices pair and communicate wirelessly, with Bluetooth using frequency-hopping spread spectrum to avoid interference and enable multiple devices to communicate simultaneously.

How does radar work?

Radar (Radio Detection and Ranging) works by transmitting microwave radio waves and detecting their reflections from objects. By measuring the time for waves to return and the frequency shift (Doppler effect), radar determines object distance, speed, and location.

How does radio work?

Radio works by transmitting information on electromagnetic radio waves. A transmitter converts sound or data into radio waves that travel through space, and a receiver picks up these waves and converts them back into sound or data.

How does WiFi work?

WiFi works by transmitting data using radio waves in the microwave frequency range (2.4 GHz and 5 GHz). A router converts digital data into radio signals that devices receive and convert back to data, enabling wireless internet access.

What are electromagnetic waves?

Electromagnetic waves are oscillating electric and magnetic fields that travel through space, transferring energy without requiring a medium. They include radio waves, microwaves, light, X-rays, and gamma rays, all traveling at the speed of light.

What are microwaves?

Microwaves are electromagnetic waves with frequencies between 300 MHz and 300 GHz, falling between radio waves and infrared radiation in the electromagnetic spectrum. They're used for communication (radar, WiFi, cell phones), cooking (microwave ovens), and scientific applications.

What is electromagnetic radiation?

Electromagnetic radiation is energy that travels through space as oscillating electric and magnetic fields. It includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays—all part of the electromagnetic spectrum, differing only in frequency and wavelength.

What is light?

Light is electromagnetic radiation that our eyes can detect, with wavelengths between about 400-700 nanometers. It behaves as both a wave and a particle (photon), traveling at the speed of light and carrying energy.

What is the difference between AM and FM radio?

AM (Amplitude Modulation) varies the amplitude (strength) of radio waves to encode information, while FM (Frequency Modulation) varies the frequency to encode information. AM is simpler but more susceptible to interference; FM provides better sound quality and is less affected by static.

What is the electromagnetic spectrum?

The electromagnetic spectrum is the full range of all possible frequencies of electromagnetic radiation, from low-frequency radio waves to high-frequency gamma rays. It includes radio, microwave, infrared, visible light, ultraviolet, X-ray, and gamma ray regions.

How do capacitors work?

Capacitors work by storing electrical charge on two conductive plates separated by an insulating material. When voltage is applied, charges accumulate on the plates, creating an electric field that stores energy. The capacitor can then release this stored energy when connected to a circuit.

What is an electric dipole?

An electric dipole is a pair of equal and opposite charges separated by a distance. It creates an electric field that points from the positive to the negative charge and has a dipole moment that measures the strength and orientation of the charge separation.

What is an electric field?

An electric field is a region around an electric charge where electric forces act on other charges. It represents the force per unit charge and describes how charges influence each other through space, even without direct contact.

What is capacitance?

Capacitance is the ability of a capacitor to store electrical energy in an electric field. It's measured in farads and represents how much charge a capacitor can store per volt of voltage applied across it.

What is Coulomb's law?

Coulomb's law describes the force between two electric charges. It states that the force is proportional to the product of the charges and inversely proportional to the square of the distance between them. Like charges repel (positive force) and opposite charges attract (negative force).

What is electricity?

Electricity is the flow of electric charge, typically electrons moving through a conductor. It involves electric current (flowing charge), voltage (electrical pressure), and can power devices and create magnetic fields.

What is static electricity?

Static electricity is the buildup of electric charge on an object's surface. It occurs when electrons transfer between objects through contact or friction, creating an imbalance of charge that can cause sparks or attraction.

What is voltage?

Voltage is the electrical potential difference between two points, representing the 'pressure' that drives electric current. It's measured in volts and determines how strongly charge is pushed through a circuit.

Why do like charges repel?

Like charges repel because they create electric fields that push away from each other. Two positive charges or two negative charges experience repulsive forces because their electric fields interact in a way that pushes them apart, following Coulomb's law which states that like charges repel with a force proportional to the product of their charges.

Why do we get electric shocks?

We get electric shocks when electric charge suddenly flows through our body. This can happen from static electricity (charge buildup discharging) or from contact with live electrical circuits, causing a painful sensation.

How do electric motors work?

Electric motors work by using electromagnetic forces—electric current in coils creates magnetic fields that interact with permanent magnets or other magnetic fields, creating forces that cause rotation. The motor converts electrical energy into mechanical work through the interaction of magnetic fields.

How do generators work?

Generators work by electromagnetic induction—rotating coils of wire in magnetic fields create changing magnetic flux, which induces electric current according to Faraday's law. Mechanical energy (from turbines, engines, etc.) rotates the coils, converting mechanical energy into electrical energy.

How do magnets work?

Magnets work through magnetic fields created by aligned magnetic domains in materials. Permanent magnets have domains aligned by their atomic structure, while electromagnets create fields through electric current flowing through coils.

How does a compass work?

A compass works because its magnetic needle aligns with Earth's magnetic field. The needle is a small magnet that points toward magnetic north, allowing navigation by showing direction relative to Earth's magnetic poles.

What is a magnetic field?

A magnetic field is a region around a magnet or moving electric charge where magnetic forces act on other magnets or moving charges. It's invisible but can be detected by its effects on magnetic materials and compasses.

What is a solenoid?

A solenoid is a coil of wire wound in a helical shape that creates a uniform magnetic field when electric current flows through it. Solenoids are used as electromagnets, with applications ranging from door locks to scientific instruments, creating strong magnetic fields in a controlled manner.

What is electromagnetic induction?

Electromagnetic induction is the process of generating electric current by changing magnetic fields. When a magnetic field changes near a conductor, it creates an electric field that drives current, as described by Faraday's law.

What is magnetic flux?

Magnetic flux is a measure of the total magnetic field passing through a given area. It's calculated as flux = magnetic field × area × cosine of the angle between field and area normal. Magnetic flux represents how much magnetic field 'flows' through a surface and is measured in webers.

Why do magnets attract metal?

Magnets attract certain metals (like iron, nickel, and cobalt) because these ferromagnetic materials have unpaired electrons that align with the magnet's magnetic field, creating attraction through magnetic forces.

Why do magnets lose their magnetism?

Magnets lose their magnetism when magnetic domains become misaligned due to heat, mechanical shock, or exposure to opposing magnetic fields. High temperatures can randomize domain alignment, while physical impacts or strong opposing fields can disrupt the ordered magnetic structure that creates magnetism.