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Biodiversity

Learning Outcomes  👉 What is biodiversity  👉 Origin of biodiversity  👉 Nature of biodiversity  👉 Interrelationships of organisms  👉 How to measure biodiversity  👉 Biodiversity of Bangladesh  👉 Risks and remedies of biodiversity  What is Biodiversity? The term biodiversity describes the great variety of life on Earth. Biodiversity refers to the variety of living things, including plants, animals, and microorganisms. We don't know for sure exactly how many different organisms there are on Earth. However, scientists estimate that there are about 8-14 million (80 to 140 lakh) different species of organisms on this Earth. Some believe that the number is higher. But whatever the number, most of these organisms are unknown to us. Only 1.2 million (12 lakh) species have been identified and described so far, most of which are insects. This means that billions of other organisms are still mysterious and unknown to us. Origin of Biodiversity The unique characteristics of all sp
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Electromagnetic Induction and Alternating Current

Electromagnetic Induction and Alternating Current Notes for Class 11 - 12

Learning Outcomes

  • Electromagnetic Induction
  • Generating Electricity with Magnet
  • Induced Electromotive Force
  • Faraday's Laws of Electromagnetic Induction
  • Lenz's Law
  • Lenz's Law and Conservation of Energy
  • Self Induction and Mutual Induction
  • Generating of Alternating Current
  • Root Mean Square Value, Peak Value and Current

Electromagnetic Induction

The process of inducing temporary electromotive force or electricity by means of a moving magnet or current-conducting coil in a closed circuit is called electromagnetic induction.

Electromagnetic induction is a phenomenon discovered by Michael Faraday in the 19th century, which explains the relationship between electricity and magnetism. It refers to the production of an electrical voltage or current in a conductor as a result of a changing magnetic field in its vicinity. This process is the basis of many important technological applications, including electric generators, transformers, and motors.

The basic principle behind electromagnetic induction is that a magnetic field that is changing with time will induce a current in a conductor that is placed within the field. This is known as Faraday's Law of Electromagnetic Induction. The amount of voltage or current induced in the conductor is proportional to the rate of change of the magnetic field, which is why rapidly changing magnetic fields produce more voltage or current than slowly changing fields.

One of the most important applications of electromagnetic induction is in the generation of electrical power. In a generator, a rotating magnetic field is created by passing an electrical current through a coil of wire. As the magnetic field rotates, it induces an electrical voltage in a separate coil of wire, which can be used to produce an electrical current. This process is repeated millions of times per second to generate large amounts of electrical power.

Another important application of electromagnetic induction is in the operation of electric motors. In a motor, a magnetic field is created by passing an electrical current through a coil of wire. When the magnetic field is placed near a permanent magnet, it creates an interaction between the magnetic fields that causes the coil of wire to rotate. This rotation can be used to perform work, such as turning a fan or driving a machine.

Transformers are another important application of electromagnetic induction. A transformer is a device that uses electromagnetic induction to convert an electrical voltage from one level to another. This is achieved by passing an electrical current through a primary coil of wire, which induces a voltage in a secondary coil of wire. The voltage in the secondary coil can be adjusted by changing the number of turns in the coil, which allows transformers to be used to increase or decrease the voltage of an electrical supply.

In conclusion, electromagnetic induction is an important phenomenon that is used in a wide range of technological applications, including electric generators, transformers, and motors. It is based on the principle that a changing magnetic field will induce an electrical voltage or current in a conductor, and is a crucial part of the generation, distribution, and use of electrical power.

Generating Electricity with Magnet

Michael Faraday for the first time postulated that electricity can be generated by using magnet. It is called Faraday's Experiment.

Generating electricity with a magnet involves using the principle of electromagnetic induction. The basic idea is to move a conductor, such as a wire, through a magnetic field or change the magnetic field around a conductor to create an electric current.

Here are the basic steps involved in generating electricity with a magnet:

Create a magnetic field: You can create a magnetic field using a permanent magnet, an electromagnet, or a solenoid. A solenoid is a coil of wire that produces a magnetic field when an electric current flows through it.

Move the conductor: Move a conductor, such as a wire, through the magnetic field, or move the magnetic field around the conductor. This movement will induce an electric current in the wire.

Collect the electricity: Connect the wire to a circuit that includes a load, such as a light bulb or a motor. The electric current will flow through the load and power it.

The amount of electricity generated depends on several factors, including the strength of the magnetic field, the speed of movement, and the number of turns in the wire. You can increase the amount of electricity generated by using a stronger magnet, moving the wire faster, or increasing the number of turns in the wire.

Generating electricity with a magnet is the basic principle behind many modern electrical devices, including generators, motors, and transformers. These devices use complex arrangements of magnets and conductors to convert mechanical energy into electrical energy or vice versa.

Magnetic flux

The product of the area of a surface and the perpendicular component of a magnetic field on the surface is called magnetic flux.

Magnetic flux is a measure of the strength and extent of a magnetic field. It is defined as the total number of magnetic field lines passing through a given surface, usually represented by a vector quantity. The unit of magnetic flux is the Weber (Wb). Magnetic flux is important in many areas of physics and engineering, including electromagnetism, electrical engineering, and materials science. It is used to calculate the amount of electromagnetic energy stored in a magnetic field and is also a key parameter in the design of electromagnetic devices such as motors and generators. The concept of magnetic flux is closely related to Faraday's law of electromagnetic induction, which states that a changing magnetic field can induce an electrical current in a nearby conductor.

Magnetic flux density

The magnetic flux density refers to the flux per unit area.

Magnetic flux density, also known as magnetic induction or magnetic field density, is a measure of the strength of a magnetic field at a particular point in space. It is defined as the magnetic flux per unit area perpendicular to the direction of the magnetic field. The unit of magnetic flux density is the Tesla (T).

Magnetic flux density is a vector quantity, meaning that it has both magnitude and direction. It is important in many areas of physics and engineering, including electromagnetism, electrical engineering, and materials science. It is used to calculate the force experienced by a moving charged particle in a magnetic field, as well as the amount of electromagnetic energy stored in a magnetic material. The concept of magnetic flux density is also used in the design of magnetic sensors and other electromagnetic devices.

Faraday's Laws of Electromagnetic Induction

In 1831, A famous scientist Faraday discovered the laws of electromagnetic induction. These laws are named Faraday's laws of electromagnetic induction.

First Law: Whenever any change in magnetic flux takes place in a closed coil, emf is temporarily induced across the circuit. Induced emf or current flow last, as long as the magnetic flux is changed. The direction in which the current flows with the increasing of magnetic flux is exactly opposite to the direction of the current flow with decreasing magnetic flux.

Second Law: Magnetic of induced electromotive force of a closed circuit is inversely proportional to the negative value of the rate of change of magnetic flux across the circuit.

Lenz's Law

The direction of the induced current or emf is such obstructing to the change of magnetic flux as causes the production of inducing current in the circuit. 

Self Induction and Mutual Induction

Self-induction

A magnetic flux associated with a coil changes due to a change in electric flow through the coil or due to a change in motion of the coil. The electromagnetic induction taking place due to change is called self-induction.

Co-efficient of self-induction

If one unit of current flows in a coil, the total amount of magnetic flux associated with the coil is called the co-efficient of self-induction.

Unit co-efficient of self induction

In S.I. system, the unit co-efficient of self-induction is henry. The units is named after the American physicist Joseph Henry.

Mutual induction

The phenomenon of electromagnetic induction produced in a secondary coil due to the non-uniform flow of current in the primary coil is called mutual induction.

Co-efficient of mutual induction

The number of magnetic flux associated with the secondary coil due to the flow of one unit of current in the primary coil is called mutual induction.

Alternating current

In a current, if the current flow changes its direction after a certain period and gains its maximum and minimum values after a certain time interval, this current flow is called alternating current.

A.C Generator or A.C dynamo

A machine by which mechanical energy is transformed into electrical energy is called generator or dynamo. Alternating current can be produced by this machine.

An A.C dynamo has the following components:

Magnet NS: This is a permanent electric magnet.

Armature or revolving coil: This is an insulated and rectangular iron bar ABCD that contains a lot of coils of wires situated at the middle of magnet.

Two slip rings or wheels: These are two special rings E and F made of metal. The rings are kept away from one another but are attached along their two ends of revolving coil. The slip rings are strongly attached with the axis around which the coil rotates. So, the rings rotate at the time of rotating of coil.

Brush: Two brushes I and J are made of carbon. These two brushes are pressed down the slip rings along a spring. An external R is connected to these two brushes.

Transformer

A machine with which the high voltage. A.C is converted into low voltage or low voltage A.C is converted into high voltage is called transformer.

There are two types of transformer: step up and step down.

Step up: A transformer which changes low potential to high potential is called step up transformer. 

Step down: a transformer which changes high potential to low potential is called step down transformer.

Use of transformer

Transformer is used in TV, Radio, Telephone, Telegraph, etc. A strong step up transformer is used is power station to increase voltage from 25000 volts to 4,00,000 volts. Again, step down transformer is used to distribute electricity at low voltage in different places.

220V line is required for household use and 440V line is for air cooler.

Electric motor

An electric motor is an electrical machine that converts electrical energy into mechanical energy. There are two kinds of electrical motors: A.C motor and D.C motor. Electric motor is used to run electric fan and pump.

Root Mean Square Value, Peak Value and Current

Maximum value of alternating current or electromotive force is called peak value.

Full cycle: A complete change of current or Pd from a particular value and to the same value in the same direction is known as a full cycle.

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