Key Principles of Electricity and Magnetism in Physics
Electricity is the motion of electric power/charge. Electricity can be obtained from renewable and non-renewable sources of energy.
Wind and water are the natural/renewable sources that help generate power by rotating turbines.
Electricity can also be obtained from various non-renewable sources viz: coal, natural gas, nuclear power, etc. These resources are considered primary/fundamental sources of energy.
‘Electromagnetism’ is a combination of electricity and magnetism, and they both are inter-related, these relations are described by Maxwell’s Equations.
In this article, we will discuss what is magnetism, what causes magnetism, and the relation of electricity with magnetism.
What is Magnetism?
Do you know what a magnet is? A magnet is a material that generates an invisible field around it called the magnetic field; this field is responsible for generating a force (magnetism) that pulls an object like iron filling towards itself; also repels the objects.
Magnetism is the property of a magnet to attract or repel objects. Like electricity, magnetism is also caused by the motion of electric charge.
Not all magnets possess the same property, they are categorized into three following forms:
Permanent Magnets
These magnets are called persistent magnets because they persist in their magnetism after the removal of the magnetic field around them. Some of the examples of permanent magnets are:
Neodymium Iron Boron (NdFeB)
Samarium Cobalt (SmCo)
Ceramic or ferrite magnets
Alnico
Temporary Magnets
These magnets are non-persistent in their magnetism retrieving attribute. These magnets have the quality to behave like their boss ‘permanent magnets’; however, they lose magnetism after the removal of the magnetic field around them. One of the examples of such type is a soft iron device like a paper clip.
Electromagnets are also referred to as temporary magnets because they possess magnetism through electricity. As soon as the power of the battery ceases, these magnets lose their magnetic property. So, what is an electromagnet?
Electromagnet
An electromagnet is made by winding the multiple loops of a wire around a current-carrying conductor. An example of this is the Solenoid.
To magnetize an electromagnet, a current is passed through the solenoid and a magnetic field generates around it. The strength of the magnetic field inside the coil is high. The magnetic field’s strength depends on the magnitude of the current and the number of turns of wire.
Let’s suppose that wire is wound around a non-magnetic material like a wooden stick, we observe that the magnetic field is not high. However, if we replace it with a ferromagnetic material like iron, the strength of magnetic field wire rises dramatically.
Overall, the strength of the magnetic field relies mainly on the magnetic material being used. Certain magnetic materials that possess varying magnetism, let’s discuss these:
Electromagnetism is a phenomenon in which electricity and magnetism are related to each other. Their relationship can be described with the help of Maxwell’s equations.
What is Magnetic Material?
The materials attract or repel the objects brought in their vicinity, according to their ability to generate the magnetic field. The response of these materials is ascertained by the magnetic dipole moment associated with their intrinsic angular momentum, or spin, of their electrons. There are three types of magnetic materials. These are:
Ferromagnetic
Diamagnetic
Paramagnetic
Ferromagnetic Materials
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These materials have some unpaired electrons in their atoms, and they generate a weak magnetic field around them because atoms (magnetic domains) inside the magnetic materials are aligned in a way that they cancel out each other, as you can see in the image above.
An external magnetic field is applied to the material to align the atoms in a way that generates the magnetic field. However, after the removal of the electric field, this material persists with its magnetism, i.e., remanence. Such examples are cobalt, diamagnetic nickel, and iron.
Diamagnetic Material
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The materials that don’t generate the magnetic field are called diamagnet because atoms in these materials have paired electrons, that’s why they don’t generate their own magnetic field.
On applying an external magnetic field to these materials, the strength of the magnetic field is so weak that it is unnoticeable. It’s because they don’t have unpaired electrons and are very less influenced by an external field.
Point to Remember:
Most of the elements in a periodic table are diamagnetic.
Paramagnetic Material
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Paramagnetic materials are less susceptible to the magnetic field. Unlike ferromagnetic materials, paramagnetic materials don’t reveal the property of remanence because they lose the property of magnetism after an external magnetic field is removed around them.
These materials bear attractive forces that are 10,000 times weaker than ferromagnetic materials, that’s why they are considered non-magnetic.
What is Magnetic Induction?
Magnetic or electromagnetic induction is the phenomenon of generating an electromotive force or EMF around the current-current conductor in a changing magnetic field. So, EMF is given by:
E = - N\[\frac{d\varphi }{dt}\]
Here,
N = no of turns of wire around the conductor
\[\frac{d\varphi }{dt}\] = flux changing with time dt
FAQs on Electricity and Magnetism Explained for Students
1. What is the fundamental relationship between electricity and magnetism?
The fundamental relationship, known as electromagnetism, is that electricity and magnetism are two interconnected aspects of a single force. A moving electric charge or an electric current will always produce a magnetic field. Conversely, a changing magnetic field will induce a voltage and create an electric current in a nearby conductor, a principle called electromagnetic induction.
2. How are electric fields and magnetic fields different?
While they are linked, electric and magnetic fields have distinct properties:
- Source: Electric fields are created by all electric charges, whether they are stationary or moving. Magnetic fields, however, are only created by moving electric charges.
- Force: An electric field exerts a force on any charge within it, regardless of its motion. A magnetic field only exerts a force on a charge that is moving.
- Field Lines: Electric field lines originate from positive charges and terminate on negative charges. Magnetic field lines are always continuous, closed loops, with no start or end point.
3. What is electromagnetic induction and how does it generate electricity?
Electromagnetic induction is the process of producing an electric current within a conductor by exposing it to a changing magnetic field. This is the core principle behind electric generators. It works when a wire coil is moved through a magnetic field, or a magnet is moved relative to the coil. This motion causes the wire to cut through magnetic lines of force, which induces a voltage and forces electrons to flow, creating an electric current.
4. What are some common real-world examples of electromagnetism?
Electromagnetism is the foundation of much of modern technology. Some key examples include:
- Electric Motors: Convert electrical energy into mechanical motion using the force on a current-carrying wire in a magnetic field.
- Electric Generators: Do the opposite of motors, converting mechanical motion into electrical energy through induction.
- Transformers: Use electromagnetic induction to raise or lower AC voltage for efficient power distribution.
- Speakers and Microphones: Convert electrical signals into sound waves (and vice-versa) using coils and magnets.
- Hard Drives: Use tiny electromagnets to read and write data onto a magnetic disk.
5. How can you create a simple electromagnet?
You can create a simple electromagnet by tightly wrapping an insulated copper wire around a ferromagnetic core, such as an iron nail. When you connect the ends of the wire to a power source like a battery, an electric current flows through the coil. This current generates a magnetic field that is concentrated by the iron core, turning the nail into a magnet. When the current is turned off, the nail loses its magnetism, which is why it is called a temporary magnet.
6. What is Fleming's Left-Hand Rule and where is it used?
Fleming's Left-Hand Rule is a mnemonic used to find the direction of force on a current-carrying conductor placed in a magnetic field. When you arrange your thumb, forefinger, and middle finger of your left hand perpendicular to each other:
- The Forefinger represents the direction of the Magnetic Field.
- The Centre (middle) finger represents the direction of the Current.
- The Thumb then indicates the direction of the Thrust or Force.
This rule is primarily applied to understand the working principle of electric motors.
7. What are the main types of magnetic materials?
Materials are mainly classified into three types based on how they interact with magnetic fields:
- Ferromagnetic: Materials like iron, nickel, and cobalt that are strongly attracted to magnets and can be permanently magnetised.
- Paramagnetic: Materials like aluminium and platinum that are weakly attracted to magnets.
- Diamagnetic: Materials like copper, gold, and water that are weakly repelled by magnets.
8. If moving charges create magnetic fields, why aren't the wires in our walls magnetic?
This is because household wiring uses alternating current (AC) with two wires running very close together. The live wire carries current in one direction, and the neutral wire carries it back in the opposite direction. Because these currents are equal and opposite, the magnetic fields they generate are also equal and opposite. At any small distance away from the cable, these two fields effectively cancel each other out, resulting in no noticeable magnetic effect.
9. Is it possible to have magnetism without a flow of electric current?
While large-scale electromagnets require a current from a power source, the magnetism in permanent magnets comes from a different kind of moving charge. At the atomic level, electrons orbiting a nucleus and their intrinsic property called electron spin act like microscopic circulating currents. In magnetic materials like iron, the spins of countless electrons align in the same direction, combining to create a strong, macroscopic magnetic field without needing an external wire or battery.
10. Why is AC (Alternating Current) preferred over DC (Direct Current) for long-distance power transmission?
AC is preferred for long-distance power transmission due to its efficiency. Power loss in wires is much lower when electricity is transmitted at very high voltages. The voltage of AC can be easily and efficiently increased for transmission and decreased for home use with devices called transformers, which operate on the principle of electromagnetic induction. Transformers do not work with DC, making it very difficult and costly to change DC voltage levels. This makes AC the practical choice for national power grids.
