# Interactive Tutorials

These demonstrations about laws and tools associated with electricity and magnetism allow you to adjust variables at and to visualize invisible forces — which makes them almost better than the real thing.

### Alternating Current

Alternating current behaves differently, depending on what components are in a circuit.

### Arc Lamp

Invented decades before it could be used, the first type of electric light was so brilliant it was used for lighthouses and street lamps.

### Audion

In 1906, American physicist Lee De Forest invented the Audion (or triode), building on John Fleming's discovery of the diode just a few years before.

### Barkhausen Effect

The Barkhausen effect makes the concept of magnetic domains audible (if not exactly music to the ear).

### Barlow's Wheel

English mathematician Peter Barlow devised an instrument in 1822 that built on advances from earlier in the century (including the invention the battery) to create a very early kind of electric motor.

### Bullet Speed

This tutorial takes a shot at explaining how circuits can be used to measure things beyond the capacity of human senses.

### Capacitor

A capacitor is similar to a battery in that both store electrical energy. But a capacitor can't actually produce new electrons; it only stores them.

### Compasses in Magnetic Fields

Experiment with the compass in this tutorial to see how it responds to magnetic fields.

### Contracting Helix

This nifty device, a kind of precursor to the Slinky, demonstrates how parallel wires attract.

### Current Flow

This tutorial illustrates how the flow of water through a system of pipes can be used to understand the flow of current through an electric circuit.

### Daniell Cell

English chemist John Frederick Daniell came up with a twist on the simple voltaic cell that resulted in a longer-lasting source of power.

### DC Motor

Electric motors turn electricity into motion by exploiting electromagnetic induction.

### Deionization

The magnets here at the lab can generate massive amounts of heat. To cool them off, we need massive amounts of water. But first, we have to take the ions out.

### Diamagnetism and Paramagnetism

Think iron, nickel and other "ferromagnetic" substances are the only ones with magnetic properties? In fact, everything reacts to magnetic fields in some way.

### Electricity Meter

When electricity became available to the masses, utilities needed meters to record customer usage. This early 20th century model resembles many in use today.

### Electromagnetic Deflection in a Cathode Ray Tube, I

Discovering how cathode rays behave in a magnetic field was a big step forward for scientists trying to understand the mysterious phenomenon.

### Electromagnetic Deflection in a Cathode Ray Tube, II

Many people interact with cathode ray tubes for part, if not most, of the day without having a clue how they work. Here's the inside scoop.

### Electromagnetic Induction

In 1831, Michael Faraday carried out numerous experiments to prove that electricity could be generated from magnetism. He not only demonstrated electromagnetic induction, but also developed a good conception of the processes involved.

### Electromotive Force in Inductors

Electromotive Force (EMF) and its sidekick, back EMF, are interesting electromagnetic phenomena that aren't really forces at all.

### Electrostatic Generator

Though simple by today's standards, the early electrostatic generators were a great milestone in humankind's understanding of electricity, allowing scientists to produce electricity so they could study it.

### Electrostatic Repulsion in Van de Graaff Bubbles

A fun look at how Van de Graaff generators illustrate electrostatic forces.

Just a year after electromagnetism was discovered, the great scientific thinker Michael Faraday figured out how to turn it into motion.

### Faraday's Ice Pail

Out of a humble ice pail the great experimentalist Michael Faraday created a device to demonstrate key principles of attraction, repulsion and electrostatic induction.

### Foucault's Disk

Léon Foucault, a French physicist much better known for his pendulum demonstrating the rotation of the Earth, also created in 1855 a device that illustrated how eddy currents work.

### Fourier Transform Ion Cyclotron Resonance (FT-ICR)

FT-ICR is a powerful type of mass spectrometry, co-invented by the Magnet Lab's Alan Marshall, particularly suited to identifying heavy molecules.

### Galvanometer

This tutorial illustrates how a galvanometer, an instrument that detects and measures small amounts of current in an electrical circuit, works.

### Guitar Pickup

Keith Richards and Eric Clapton owe their fame and fortune (in part) to electromagnetic induction.

### Hall Effect

When a magnetic field is applied perpendicular to the flow of current, the field causes resistance in the current. This is the Lorentz force at work, and can be observed well in the Hall effect.

### Heat Resistance

Heating a metal conductor makes it more difficult for electricity to flow through it. See why in this tutorial.

### Ignition Coil

Ladies and gentlemen, start your engines and learn about the ignition coil, a type of step-up transformer key (no pun intended) to the operation of your car.

### Induced Current

A current can be induced in a conducting loop if it is exposed to a changing magnetic field.

### Inductive Pendulum

Get the swing of electromagnetic induction with this simple tutorial.

### Inductive Reactance

Like resistance, reactance slows an electrical current down. Explained by Lenz's Law, this phenomenon occurs only in AC circuits.

### Kelvin Water Dropper

The legendary Lord Kelvin made electricity from water with this ingenious electrostatic generator.

### Leyden Jar

These devices, though quite humble, represented a tremendous breakthrough in the history of electricity; they were the first capacitors, and as such were able to store electric charge.

### Lissajous Figures on an Oscilloscope

This tutorial is a three-dimensional simulation of a cathode ray oscilloscope producing Lissajous figures as it compares sinusoidal voltages.

### Lodge's Experiment

Sir Oliver Lodge's experiment demonstrating the first tunable radio receiver was an important stepping stone on the path toward the invention of a practical radio.

### Lorentz Force

Learn the Lorentz force with the help of this tutorial, in which a wire fashioned into a pendulum moves inside a magnetic field.

### Magnetic Core Memory

Magnetic core memory was developed in the late 1940s and 1950s, and remained the primary way in which early computers read, wrote and stored data until RAM came along in the 1970s.

### Magnetic Domains

In ferromagnetic materials, smaller groups of atoms band together into areas called domains, in which all the electrons have the same magnetic orientation. That's why you can magnetize them. See how it works in this tutorial.

### Magnetic Field Around a Wire, I

Whenever current travels through a conductor, a magnetic field is generated.

### Magnetic Field Around a Wire, II

A handful of iron filings helps visualize the invisible magnetic field that circulates around a wire with a current running through it.

### Magnetic Field of a Solenoid

You can create a stronger, more concentrated magnetic field by taking wire and forming it into a coil called a solenoid.

### Magnetic Resonance Imaging (MRI)

In MRI, magnetic fields and radio wave pulses combine to get a unique, and medically beneficial, response from your body's hydrogen atoms. Take a peek in this tutorial.

### Magnetic Shunt

Magnetic shunts are often used to adjust the amount of flux in the magnetic circuits found in most electrical motors.

### Mass Spectra

The mass spectrum of a material, deduced using a machine called a mass spectrometer, reveals how many isotopes of a given element are to be found in the material. See here what these spectra look like and how they are useful.

### Mass Spectrometer (Dual Sector)

Mass spectrometers are machines that give scientists a look at the composition and origin of a material by analyzing and quantifying its atoms and molecules. This tutorial shows how a dual sector mass spectrometer works.

### Mass Spectrometer (Single Sector)

Mass spectrometers are machines that give scientists a look at the composition and origin of a material by analyzing and quantifying its atoms and molecules. This tutorial shows how a single sector mass spectrometer works.

### Microwaves

What makes those kernels pop inside your microwave? A whole lot of water interacting with a whole lot of high-frequency electromagnetic waves.

### Mirror Galvanometer

Invented by William Thomson (who later became Lord Kelvin for such clever acts as this), the mirror galvanometer was a useful instrument that played a key role in the history of the telegraph.

### Oersted's Compass

In 1820, Hans Christian Ørsted discovered the relationship between electricity and magnetism in this very simple experiment.

### Oscillator

Oscillators are a type of circuit found in many types of electronic equipment, including clocks, radios and computers.

### Parallel Wires

A pair of parallel wires serves to illustrate a principle that French Scienist André-Marie Ampère was the first to comprehend, back in 1820.

### Pixii Machine

This “magneto-electric machine” was the first to turn motion into electricity.

### Rheostat

After discovering the nature of electrical resistance, scientists devised instruments like this one to measure and control it.

### Right and Left Hand Rules

No fancy movement in this tutorial, but these rules come in very handy when trying to understand some of what’s going on in our other tutorials.

### Simple Electrical Cell

The simple voltaic (or galvanic) electrical cell is the most basic type of "wet" cell and demonstrates the fundamental chemistry behind batteries.

### Tape Recorder

Two heads — or even three — are better than one when it comes to understanding how tape recorders exploit electromagnetic induction.

### Transformers

Transformers are devices that transfer a voltage from one circuit to another circuit via induction.

### Transmission Lines

Electricity goes through some ups and downs on its way from the power plant to your house. Here's how it works.

### Van de Graaff Generator

Invented around 1930, the Van de Graaff generator is a popular tool for teaching the principles of electrostatics. Others just call it "that thing that makes your hair stand on end." See how it works here.

### Voltaic Pile

Italian scientist Alessandro Volta was the first to recognize key principles of electrochemistry, and applied those principles to the creation of the first battery, a simple tool which came to be known as the voltaic pile.

### Wheatstone Bridge

This circuit is most commonly used to determine the value of an unknown resistance to an electrical current.