Can We Produce Magnetism From Electricity?
Magnetism and electricity are intrinsically linked phenomena that have fascinated humans for centuries. While static electricity and natural magnets like lodestones have been known since ancient times, it took many years of scientific investigation and discovery to understand the deep connection between electricity and magnetism.
Experiments by Hans Christian Oersted, Andre-Marie Ampere, Michael Faraday, James Clerk Maxwell and others in the 19th century revealed that electric currents produce magnetic fields. This key insight enabled the invention of electromagnets, motors, generators and many other devices that use magnetism created by electricity. Today, the interplay between electricity and magnetism is essential for power generation and transmission, motors, wireless communications, computer memory and many everyday technologies. An understanding of electromagnetism underpins our technological civilization.
Early Discoveries Linking Electricity and Magnetism
The connection between electricity and magnetism was first accidentally discovered in 1820 by Danish physicist Hans Christian Oersted. During a lecture demonstration, Oersted noticed that an electric current flowing through a wire deflected a nearby compass needle. This groundbreaking observation revealed that electric currents produce magnetic fields, establishing for the first time that electricity and magnetism are linked phenomena.
Oersted’s serendipitous finding paved the way for further research and discoveries into electromagnetism. André-Marie Ampère built upon this work by showing that two parallel wires carrying electric currents attract or repel each other, depending on whether the currents are flowing in the same or opposite directions. Several years later, Michael Faraday demonstrated that moving a magnet through a coil of wire induced an electric current in the coil. These pioneering investigations revealed the bidirectional relationship between electricity and magnetism.
How Electric Currents Produce Magnetic Fields
When electric current flows through a conductor, such as a wire, it produces a magnetic field perpendicular to the direction of the current flow. This phenomenon is described by Ampere’s Law which states that the magnetic field strength around a current-carrying conductor is proportional to the amount of current flowing through it.
The direction of the magnetic field can be determined using the “right-hand rule”. If you point the thumb of your right hand in the direction of the current flow, your fingers will curl in the direction of the magnetic field lines around the wire. The magnetic field forms circular loops around the conductor, with the direction of the field determined by the direction of the current flow.
For example, if current is flowing vertically upwards through a straight wire, the right-hand rule shows that the magnetic field will form concentric circles around the wire in the clockwise direction when looking down on the wire from above. The magnetic field is strongest closest to the wire and weakens with increasing distance from the wire.
The strength of the magnetic field depends on the amount of current – a larger current will produce a stronger magnetic field. Doubling the current through the wire will double the strength of the magnetic field at any given distance from the wire. This relationship allows us to control and produce magnetic fields of varying strength by varying the electric current in a conductor.
Electromagnets
Electromagnets are a type of magnet where the magnetic field is created by an electric current. Unlike permanent magnets, the strength of electromagnets can be rapidly changed by controlling the amount of electric current.
Electromagnets consist of a coil of wire wrapped around a core made of a magnetic material like iron. When electric current passes through the wire, it creates a magnetic field. The magnetic field gets concentrated and amplified by the iron core, creating a strong magnetic field.
The magnetic field strength of an electromagnet depends on the number of wire coil turns, the current flowing through it, and the material making up the core. Electromagnets can be turned on and off by completing or interrupting the circuit supplying current to the electromagnet.
Some common uses of electromagnets include lifting heavy metal objects like cars in scrapyards, MRI machines which use strong magnetic fields to image the body, and particle accelerators that use magnetic fields to steer and focus beams of charged particles.
Compared to permanent magnets, electromagnets can generate stronger magnetic fields, but require continuous power to maintain the magnetic field. However, the ability to turn electromagnets on and off allows for greater control and more varied applications.
Maxwell’s Equations
In the 1860s, Scottish physicist James Clerk Maxwell developed a unified theory that described electricity, magnetism, and light as manifestations of the same phenomenon. Maxwell’s equations are a set of four differential equations that describe how electric and magnetic fields are generated and altered by each other and by electric charges and currents. These elegant mathematical equations fully incorporate the interplay between electrical and magnetic forces.
The four Maxwell’s equations can be written in integral form or differential form. The integral form relates fields to their sources – charges and currents. The differential form describes how those fields vary from point to point in space and time. Together, the equations describe the basic laws of classical electromagnetism.
Maxwell’s equations are:
- Gauss’s law for electricity
- Gauss’s law for magnetism
- Faraday’s law of induction
- Ampere’s circuital law with Maxwell’s addition
These four elegant equations fully capture everything about classical electromagnetism. They describe how electric and magnetic fields are generated and altered by each other and by electric charges and currents.
Maxwell’s equations unified electricity, magnetism and optics. His work showed that electric and magnetic fields travel at the speed of light and that light itself is an electromagnetic wave. This revelation that light is an electromagnetic phenomenon completed the classical unification of electromagnetism.
Electromagnetic Induction
Electromagnetic induction describes how a changing magnetic field can induce an electric current to flow in a conducting material. According to Faraday’s law of induction, when the magnetic flux through a circuit changes, an electromotive force is generated. This process allows electric generators to convert mechanical energy into electricity.
For example, in a generator coil, when a magnet is moved in and out of the coil, the changing magnetic flux induces a voltage in the coil. The induced emf drives electrons through the coil, producing an electric current. Generators operate continuously by rotating magnets within coil windings to generate a steady electric current for powering electrical devices.
Transformers also rely on electromagnetic induction between two separate coils to increase or decrease AC voltages for efficient power transmission. So in summary, the process of electromagnetic induction allows us to generate electricity from magnetism and convert voltages through transformers, enabling long-distance transmission and powering electrical devices.
Generators
One of the most important applications of electromagnetism is using electromagnetic induction to generate electricity. This is done through generators, which convert mechanical energy into electrical energy.
Generators work based on Faraday’s law of electromagnetic induction. When a conductor moves through a magnetic field, it causes electrons in the conductor to move, generating an electromotive force and inducing a voltage. This voltage creates an electric current in the conductor, producing electricity.
In generators, the conductor is typically a coil of wire rotated in a magnetic field. As it spins, the magnetic flux through the coil changes, inducing a voltage across the generator’s terminals. The faster the coil spins and the stronger the magnetic field, the greater the induced emf and electrical power that is generated.
Nearly all electrical power on Earth is generated this way. Generators are used in power plants to produce electricity from mechanical power derived from wind, falling water, steam turbines, or internal combustion engines. Portable generators also utilize small gasoline engines to turn generators and produce electricity.
The discovery of electromagnetic induction and the invention of generators to harness this phenomenon has truly transformed modern civilization, enabling widespread distribution and use of electrical power around the world.
Motors
Motors work on the principle of electromagnetic induction, which is the production of voltage or electromotive force (emf) in a conductor due to a change in the magnetic field around it. Electric motors take electrical energy and convert it into mechanical energy in the form of rotational motion.
In a typical DC electric motor, electricity from a battery flows through a coil of wire (called the armature) located within a magnetic field. This creates a force that causes the armature to rotate. Brushes connect the rotating armature to the stationary battery to provide continuous electric current. The armature contains electromagnets that get polarized by the electric current, creating magnetic poles that push and pull against the magnetic field, spinning the armature. Commutators switch the direction of the electric current to reverse the magnetic poles, keeping the armature rotating.
AC motors work in a similar manner, but use alternating current instead of direct current. The speed at which the armature rotates depends on the frequency of the AC supply and the number of magnetic poles in the motor. AC induction motors are very common and consist of a rotating magnetic field generated by the stator (stationary outside part) and a rotating armature. The changing magnetic field induces a current in the armature, creating torque.
Electric motors have enabled the automation of many mechanical processes and are used extensively in home appliances, power tools, electric vehicles, and industrial machinery. Their ability to convert electrical energy into rotational motion via magnetism is essential for modern technology.
Everyday Applications
Electromagnets and electric motors have become integral to modern life. Here are some common examples of how we utilize electromagnetism on a daily basis:
Speakers and microphones – Speakers contain electromagnets that move a cone back and forth to produce sound waves. Microphones reverse this process, using a diaphragm that vibrates in a magnetic field to induce an electric current.
Electric guitars – The pickups on an electric guitar contain magnets that detect the vibration of the guitar strings and convert it into an electrical signal that gets amplified.
MRI machines – MRI scanners use powerful electromagnets to align the protons in our body. Radio waves are then used to disturb the alignment of these protons and detect the energy released as they realign in the magnetic field.
Hard disk drives – Data is stored on the spinning disk of a hard drive magnetically. The read/write head is guided by electromagnets to precisely access data on the disk.
Maglev trains – Maglev (magnetic levitation) trains use electromagnets to lift and propel the train above the track, eliminating friction and allowing extremely high speeds.
Electric motors – Electrical energy is converted into mechanical rotation by electric motors used in appliances, power tools, electric cars, and numerous other machines we use every day.
Conclusion
Electricity and magnetism are intimately linked to one another. We have seen throughout this article how electric currents produce magnetic fields, which is the foundational principle behind electromagnets, generators, motors, and many other applications. Through the pioneering work of scientists like Oersted, Ampere and Faraday, we discovered that electricity and magnetism are two sides of the same underlying electromagnetic force. Maxwell’s equations beautifully summarize these deep connections. The generation of electricity from magnetism, known as electromagnetic induction, underpins the operation of generators, whereby mechanical energy is converted into electricity. Electric motors in turn allow us to convert electricity back into mechanical work. Our modern society is built on the widespread ability to interconvert electricity and magnetism for power generation, electric devices and transportation systems. While electricity and magnetism may seem distinct at first glance, a deeper look reveals they are intrinsically woven together.
