Electricity and Magnetism: Definition, Magnetic Material & Induction

Electricity and magnetism are two aspects of the same concept. The reason is, a changing electric field creates a magnetic field, and a changing magnetic field creates an electric field. Without using technical terms it is difficult to explain the interactions of electricity and magnetism.

• Electricity is the movement of electrical energy or charge. Static and dynamic are the two classifications.
• Magnetism is the property of a magnet to attract or repel objects. It is also caused by the motion of electric charge.
• The combined effect of electricity and magnetism is known as Electromagnetism, and they both are interrelated, their relations are described by Maxwell’s Equations.

Key Terms: Electricity, Electromagnetism, Magnetism, Magnet, Magnetic field, Electromagnet, Static electricity, Energy, Insulator, Solenoid, Electric field, Maxwell's Equation

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What is Electricity?

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Electricity is the flow of electrical charge or power. Electricity is the most widely used form of energy and a basic part of nature.

• Electricity can be either static or dynamic.
• Static electricity is due to the build-up of electrical charge on the surface of an object.
• These charges remain at rest on the surface.
• Dynamic electricity is due to the motion of the electric charges.

The ability of an atom to gain or lose an electron is determined by its valence, which in turn defines the atom's chemical and electrical properties. Depending on the ability of the material to produce free electrons, it can be classified as a conductor, semiconductor, or insulator. A larger current can be conducted in a material that has a large number of free electrons available.

Conductors 

The outer orbits of the atoms in these materials have a few loosely attached electrons. Heat energy has the potential to induce electrons in the outer orbit to break away and drift around the substance. Examples- Gold, Silver, etc

Insulators 

These are materials that don't conduct electricity very well, if at all. Atoms in these materials do not create free electrons under normal conditions. Because there are no free electrons in the substance, electrical current cannot flow through it. Examples- Glass, ceramics

Read More: Difference Between Conductors and Insulators

Semiconductors 

This substance has features of both conductors and insulators, in that it is neither conductor or insulator. Example- silicon and germanium.

Read More: Semiconductors

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What is Magnetism?

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The ability of a magnet to attract or repel items is known as magnetism. The attraction or repulsion that arises between electrically charged particles because of their motion is called magnetic force. 

• A magnetic field is a field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials.
• A magnet is a material that generates an invisible field around it called a magnetic field and this field generates a force which is called magnetism that pulls objects like iron toward itself
• It is important to note that electricity can exist without magnetism but magnetism cannot exist without electricity.

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Types of Magnets

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It is important to note that all magnets do not possess magnetic properties, therefore, based on this magnets are classified into the following types:

Permanent Magnets 

These magnets are known as persistent magnets because they retain their magnetism even when the magnetic field around them is removed. Alnico, Ceramic, etc are a few examples of permanent magnets.

Temporary Magnets 

The magnetism retrieving property of these magnets is non-persistent. They lose their magnetism as the magnetic field around them is removed.

Electromagnets 

Electromagnets are made up of winding many loops of wire around a current-carrying conductor. The Solenoid is an example of electromagnet. A current is sent through the solenoid to magnetize an electromagnet, which creates a magnetic field surrounding it. The magnetic field inside the coil has a high strength. The strength of the magnetic field is determined by the current magnitude and the number of wire turns.

Some of the uses of electromagnets are:

• Headphones and loudspeakers
• Magnetic locks
• Particle accelerators
• Transformers, motors, and Generator
• Electromagnet uses in the home include an electric doorbell, electric fan, and induction cooker.

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Magnetic Field

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Magnetic fields cannot be seen or touched. Like in cases of gravitational force, we can feel a force on ourselves, the case is not the same with magnetic field force. We do not feel it in a direct way but we are aware of its existence through its effect on other subjects. 

A magnetic field is an area in the vicinity of a magnet or a current-carrying conductor where its magnetic influence can be felt.

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Electromagnetism

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Electromagnetism is the study of the electromagnetic forces that exist between electrically charged particles and are transported by electromagnetic fields made up of electric and magnetic fields. Electromagnetic radiation, such as light, is produced by it. 

The field handles specific situations of static charge distributions (electrostatics), time-independent current distributions (magnetostatics), and electric and magnetic characteristics of matter by employing vector calculus methods to solve static and dynamic aspects of electromagnetic fields (dielectrics and magnetic media).

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Difference Between Electricity and Magnetism

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The differences between electricity and magnetism are:

• The existence of magnetic fields is the primary distinction between electricity and magnetism.
• Only when there are moving charges as a result of electricity can magnetism be felt, whereas electricity might be present in a static charge.
• Magnetism cannot exist without electricity, but electricity cannot exist without magnetism.

Electromagnetic Induction

When a magnetic field and a current-carrying conductor move relative to one another, the conductor crosses the magnetic lines of force in the magnetic field, this is known as electromagnetic induction.

The phenomenon of creating an electromotive force or EMF around a current-current conductor in a changing magnetic field is known as magnetic or electromagnetic induction. So, EMF is given by:

E = - N dφ/ dt

Here,

N = the number of wires turns around the conductor

dφ / dt = flux changing with time dt

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Magnetic Field Solenoids

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Magnetic Field and Straight Solenoid

A Straight Solenoid produces a magnetic field.

I B = 0nI at any point within the solenoid, where n is the number of turns per unit length.

(ii) At the solenoid's ends, B = 1/2 0nI

Magnetic Field and Toroidal Solenoid

Toroidal Solenoid produces a magnetic field.

I Inside the toroidal solenoid, B =0nI, here, n =N/2r, N= total number of turns (ii) Outside the toroidal solenoid, B=0nI, here, n =N/2r, N= total number of turns

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Things to Remember

• Electricity is the flow of electrical charge or power.
• The ability of a magnet to attract or repel items is known as magnetism.
• The SI unit of the magnetic field is Tesla (T).
• The relationship between μ_o, ε_o, and c is \(\frac{1}{\mu_0\epsilon_0} = c^2\), where, c is the velocity of light, ε0 is the permittivity of free space and μ_o is magnetic permeability.
• Electromagnets are made up of winding many loops of wire around a current-carrying conductor.
• The phenomenon of creating an electromotive force or EMF around a current-current conductor in a changing magnetic field is known as magnetic or electromagnetic induction.

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