What is Magnet?
Magnet is a material that has a tendency to attract magnetic materials like iron, Cobalt, Nickel, etc. First of all people of Greeks have seen that black ore of iron attracts magnetic material towards it which is now called magnetite. This type of magnet is called a natural magnet. Today Different types of magnets are available in the markets. These all magnets are made by mixing different types of material.
Concept of Magnetic field
The surrounding area of a magnet in which a magnetic material can experience either a force of attraction or repulsion is called a magnetic field. It is a vector Quantity represented by Vector B.its SI unit is Wb/m2 and is called Tesla.Magnetic Effect of Electric Current
In 1820 Oersted found that when an electric current passes through a conductor then a magnetic field is created around the current-carrying conductor. This experiment has established a relation between electric current and magnetic field.
Imagine you are holding the conductor with the palm of your right hand such that the fingers encircle the conductor and your thumb points in the direction of the current. then the direction of the fingers encircling the conductor gives the direction of the magnetic lines of force around it.
When an electric current passes through a conductor then a magnetic field appears around the conductor. this is called the magnetic effect of electric current.
Oersted's Experiment
In 1820 oersted has done an experiment to find out the existence of a magnetic field around the current-carrying conductor which is known as the magnetic effect of electric current. According to the oersted experiment, a needle magnet NS is taken and this needle magnet is kept parallel to a current-carrying conductor. when there is no electric current flowing through the conductor then there is no deflection in the position of the needle magnet. But when current is allowed to flow through the conductor then we found that the needle magnet gets deflected from its initial position. As soon the current flowing through the conductor is stopped the needle magnet takes its previous position. this experiment proved that the current-carrying conductor produces a magnetic field. On reversing the direction of electric current, the direction of the magnetic field is also reversed. Since the Magnetic field is a vector quantity then its direction is also required to find and to find the direction of the magnetic field Maxwell Right Hand Thumb Rule is used.
Magnetic field lines
it is a concept that is used to determine the direction of the magnetic field. The concept of magnetic field lines is the first time used by Michel Faraday to explain the behavior of the magnet. In reality, there is no such kind of field line that exists. it is a concept only. it is assumed that magnetic field lines originate from the North Pole and terminate at the South Pole. The figure given below shows the Concept of the magnetic field.
Properties of Magnetics Field Lines
- These field lines make a closed loop. These field lines originate from the north pole and terminate at the south pole of the magnet.
- Where the magnetic field lines are high their magnetic field strength is high.
- Two or more than two magnetic field lines never intersect each other.
Right-Hand Thumb Rule
this rule is used to find out the direction of the magnetic field associated with a current-carrying conductor.
What is Solenoid?
When a fine wire of conductors like copper or aluminum is mounted over the surface of insulator material then it is known as a solenoid. when an electric current is allowed to flow through the conductor then there is an induced magnetic field that is shown around the solenoid. The nature of this induced magnetic field is similar to the nature of the magnetic field around the current-carrying conductor.
What is an electromagnet?
When an iron piece is kept inside the solenoid then this iron piece is called a chord and it behaves like a permanent magnet hence it is called an electromagnet. when Supplying electric current is switched off then induced magnetism is lost hence electromagnet is not a stable or permanent magnet.Uses of electromagnet
Since induced magnetism in the electromagnet is a function of electric current hence it can be increased as much as we want. Due to this electromagnet is used to lift heavy metal or bodies in a crane machine.- it is used in electric bells
- it is used in microphones
- it is used in loudspeakers
Force On a Current-Carrying Conductor Placed in a Magnetic Field
When a current-carrying conductor is kept in a magnetic field then this current-carrying conductor experience a force. this force is called Lorenz's force. it was the first time discovered by the Oersted experiment. Since Force is a vector quantity then it is necessary to find out it's direction. The direction of this experienced force is found by using Fleming's Left Hand Rule. This Principle is used to make an electric motor.
Electric Motor
it is an electrical machine that converts electrical energy into mechanical energy.Construction of Electric Motor
There are two main parts of the electric motor. One is the Rotating Part and the other is the Static Part. The static part of the motor consists of a permanent magnet to produce a magnetic field Coils are mounted on the rotor and the endpoint of the coil is connected to the external power supply by using a Carbon brush. As shown below in the figure.
Working Principle of Electric Motor
When an external current is given to the rotor by a carbon brush then the coil on the rotor experienced a force and tries to put in a region where there is no magnetic field but the construction of the rotor is done in such a way that the rotor always experiences a force and hence rotate continuously.
Electromagnetic Induction
As we have seen that there is a relation between electric current and magnetic field. From Oersted Experiment we have seen that an electric current can produce a magnetic field then it is also possible that the magnetic field can also produce an electric current. The induction of electric current by the magnetic field is known as electromagnetic induction. This Principle was first time discovered by Bristish Scientist Miachel Farady. According to Electromagnetic InductionWhen, there is a relative motion between the conductor and the magnetic field then an emf is induced across the terminal of the conductor and when a load is connected across the conductor the there is current start to flow in the conductor. The direction of the induced Electric Current is Calculated by using Fleming's Right-Hand Rule. Using this Principle Electric Generator is Constructed.
Electric Generator
Electric Generator is an electrical machine that Converts Mechanical Energy into Electrical Energy. The conversion of mechanical energy into electrical energy takes place as a function of the magnetic field. Without magnetic field involvement, it is not possible to produce electricity.Construction of Electric Generator
The construction of an electric generator is similar to the Construction of an electric motor, but the difference is only power flow. Same as that the electric motor there are two main parts of the electric generator. One is the static part and the other is the Rotating part but here rotating part is called Armature. A strong magnet is kept in the stator of the motor which produces a magnetic field in the stator. A coil of many turns is mounted on the rotor and the endpoint of each coil is connected to the rotor shaft on a circular ring and a carbon brush is connected to this ring to collect induced current.
Working Principle of Electric Generator
When the armature is rotated by an external mover then the induced magnetic fields line is cut by the armature conductor and due to electromagnetic induction an EMF is induced in the armature conductor and when these conductor's terminals are connected to the external load then a current start to flow in the conductor. As shown in the given figure above.
