Electrical

Difference between the electric circuit and magnetic circuit

Explain about the Electric circuit

A simple electric circuit consists of a voltage source, some kind of load, and a conductor between the voltage source and the load to allow the flow of electrons. There is a fundamental relationship exists between current, voltage, and resistance in an electric circuit. In the following circuit, a battery acts as the voltage source, an electrical wire is used for the conductor, and light acts as a load. A switch has been introduced into this circuit. Always there should be a complete path for current to flow. If the switch is open, the path is incomplete and the light will not illuminate. Closing the switch completes the path, allowing electrons to leave the negative terminal and flow through the light to the positive terminal, shown in the figure below.

Basic Electric Circuit

Schematic Diagram

The following schematic is a representation of an electrical Schematic circuit, consisting of a cell, a resistance, a voltmeter, and an ammeter. The ammeter is connected in series with the circuit, this will indicate the amount of current flow in the circuit. The voltmeter connected across the resistance will show the value of the voltage supplied to the load.

Electric circuit with Ammeter and Voltmeter

Ohms law of Electric circuit:

Ohms law states that current through a conductor between two points is directly proportional to the voltage across those two points.

V=Voltage, I=current, R =Resistance

V=I * R

I=V/R

R=V/I

Ohms law representation

What is meant by Magnetism?

 A substance is said to be a magnet if it has a property of magnetism that means if it has the power to attract substances such as Iron, Steel, Nickel, or Cobalt known as magnetic material.

The point of maximum attraction is called magnetic poles, all magnets have at least two poles. The point that faces toward northward is called the north pole and the point face toward the southward is called a south pole.

Magnetic pole representation

Various characteristics of magnetic lines of force can be described as follows

  1. Magnetic lines of force are continuous and will always form closed loops.
  2. Magnetic lines of force will never cross one another.
  3. Parallel magnetic lines of force traveling in the same direction repel one another,
  4. Parallel magnetic lines of force traveling in opposite directions tend to unite with each other and form into single lines traveling in a direction determined by the magnetic poles creating the lines of force.
  5. The magnetic lines of force existing between two unlike poles cause the pole to be pulled together.
  6. Magnetic lines of force pass through all materials, both magnetic and Nonmagnetic.

What is meant by Magnetic Field?

The space surrounding a magnet in which the magnetic force acts is called Magnetic Field.

Michael Faraday visualized the magnetic Field as being in a state of stress and consisting of a uniformly distributed line of force.

What is meant by Magnetic Flux?

The Entire quantity of magnetic lines surrounding a magnet is called Magnetic flux. Flux in a magnetic circuit can be directly compared  to current in an electric circuit

What is meant by Magnetic Flux Density?

The number of lines of force per unit area is called flux density and is measured in line per square Inch or lines per square centimeter

B=Flux.

ɸ= Total number of lines of Flux.

A=cross sectional area of the magnetic Circuit. B   = ɸ/A

What is meant by the Magnetomotive force?

The ability of a coil to produce magnetic flux is called Magnetomotive force.

The amount of flux density in a core will depend upon five factors- The Current, Number of turns, Material of the magnetic core, Length of the core, and Cross-sectional area of the core.

More current and the more turns of wire we use, the greater will be the magnetizing effect.

MMF =N*I ampere-turns

N=Number of turns in the coil.

I=Electric Current through the circuit

What is meant by Magnetic Field intensity?

When the number of turns of wire carrying current, the MMF created in the circuit is Ni ampere turns with l representing the mean path length for the magnetic flux, the magnetic field intensity is

Magnetic Field Intensity H = Ni/l ampere-turns/meter.

                                              B= µ H

What is meant by Magnetic Circuit?

The magnetic circuit is nothing but the path of magnetic flux, the MMF of the circuit creates flux in the path against the reluctance of the path.

Flux = mmf/Reluctance

Magnetic Circuit representation

Ohms law of Magnetic circuit

The MMF of a magnetic circuit is directly proportional to flux established in it provided no part of the magnetic circuit is saturated, the constant of proportionality is the reluctance of the magnetic circuit   MMF α flux or MMF = Flux X Reluctance

Difference between an Electric circuit and a magnetic circuit

Electric CircuitMagnetic circuit
 The closed path for electric current is called as Electric CircuitThe closed path for magnetic flux is called a Magnetic Circuit
Current= emf/Resistance Emf=voltageFlux= MMF/Reluctance
Unit of current (I) is measured in amperesUnit of flux (ϕ) is measured in weber (wb)
Electromotive force is the driving force and is measured in Volts(V). Emf= ∫ E. dlMagnetomotive force is the driving force and is measured in Ampere Turns (AT)  mmf=∫ H. dl
The electric line of flux is not closed, they start from a positive charge and end on a negative charge.Magnetic lines of flux are closed lines They flow from N pole to S pole externally while S pole to N pole internally.
Resistance opposes the flow of the current R=ρ*l/a and measured in (AT/wb) R=Resistance ρ  = Resistivity l= Length of wire a=Area of cross-sectionReluctance opposes the flow of magnetic flux S= l/µo µr and measured in Ω S=Reluctance l=length of magnetic path in meters µo =permeability of free space (vacuum) = 4 π × 10-7 henry/meter µr= relative permeability of a magnetic material A= cross sectional area of square meters Reluctance(S)=mmf/Flux  = F/Ø  
Conductance = 1/ResistancePermeance= 1/Reluctance
Conductivity (σ) The property of a component that describes how the electric current in the component is related to the electrical potential difference (voltage) across it.Permeability (μ) Ratio of the magnetic induction to the magnetic intensity. It is used to measure a material’s resistance to the magnetic field or measure the degree to which a magnetic field can penetrate through a material.
Current density (δ)=l/a I=current a= Area of cross-sectionFlux density(B)= Ø/a =Flux, a= Area of cross-section
Electrical Field intensity(E) E= emf/Q emf= Electromotive force, Q=chargesMagnetic Field Intensity(H) H=mmf/l  MMF =Magnetomotive force I=Average length of the path (m)
Electromotive force Quantity tends to cause a movement of charges around a circuit, the direction is that of movement of positive charges. Emf is measured by the amount of energy developed by transfer of unit positive charge                         Magnetomotive force Along any path, the line integral of the magnetic field strength along that path, If the path is closed the line integral is equal to the total magnetizing current in ampere-turns.
Mmf drop = ϕSVoltage drop=IR
In an electric circuit, electric current flows in the form of electrons.In a magnetic circuit, molecular poles are aligned, the flux doesn’t flow but sets up in the magnetic circuit.
In a series circuit Current in all elements is the same, but voltage or emf is different across each element in the circuit.In a series circuit, the Same flux passes through all elements in series, and the sum of MMF’s across the elements is equal to the applied MMF.
In a parallel circuit Voltage across all branches is the same and equal to applied voltage whereas the current in the branches is different.In a parallel circuit, the MMF of each branch is the same and equal to the applied MMF. Flux in each branch is different and their sum equals the resultant flux.
When current flows, the energy is spent continuouslyEnergy is needed only to create the flux but not to maintain it.
Number of Electric Insulators, Air is a very good insulator and current can’t pass through itThere is no magnetic insulator, Flux can be set up even in the air.
Kirchhoff current law and voltage law is applicable to the electric circuitKirchhoff MMF law and flux law are applicable to the magnetic flux.
Representation of electric circuit


Representation of magnetic circuit

Difference between electric and magnetic circuit

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