Home Electromagnetism Various Types Of Solenoids

Various Types Of Solenoids


A solenoid consist of insulating long wires and these insulating long wires are bonded closely in the form of a helix. The length of insulating long wires in the solenoid is very long in comparison to their diameters. The magnetic field outside the solenoid is always zero because the net magnetic field due to each loop is present in the solenoids.

Inside the solenoid, all the magnetic fields of the individual loop are in the same directions. So the net magnetic field does not become zero but outside the solenoid, individual magnetic fields are in opposite directions and this is the reason why the magnetic field outside the solenoid is zero.

Magnetic Field Due To A Current-Carrying Solenoid On Its Axis –

Consider a long solenoid of length l and n number of turns in which current is flowing. We want to find out the magnetic field inside the solenoid as the magnetic field outside the solenoid is zero. Consider a rectangular loop of length l and width b. Let P q r s are the points on the loop. n equal to the number of turns per unit length and magnetic field on the axis of the solenoid is equal to the multiplication of ‘Uo’, current I and number of turns per unit l.

Note – Magnetic field near the ends of the solenoid is found to be uoNI/2.

Toroid- If a solenoid is bent into the form of the circle and the ends of the solenoid are joined together. This is called a toroid.

Magnetic Field On The Axis Of A Toroid-

Consider a toroid that has inner radius R1 outer radius R2. blood and number of turns are present in toroid and current flows through the wires are I. To find the magnetic field we assume a circular loop of radius r in which there are three situations.

Note 1. If young’s double slits experiment perform in a medium of the refractive index then B(Medium) is equal to B(air) divided by u.

Note 2. Fringe width is directly proportional to the distance between the slits and the screen.

Note 3. Fringe width is inversely proportional to the distance between the slits.

Note 4. If white light is used in young’s double-slit experiments then in a fringe pattern different colors are seen.

Note 5. As fringes a distance depends on wavelength for red color is maximum is greater than violet then the distance of violet fringes is lesser than the red color. So in the fringes pattern violet color will be nearest while red color is far.

Condition For Sustained Interference-

  1. For sustained interference both the sources should be coherent sources for which the phase difference between the sources or waves should be constant with respect to the time.
  2. The frequency and wavelength of the waves should be equal for sustained interference.
  3. The amplitude of waves should be equal so to achieve perfect contrast on the screen.
  4. The path difference between the waves should not be larger. Otherwise, the probability of reaching waves from different sources at a single point And at the same time will be minimum.


when two or more waves of the same frequency and similar amplitude superimpose on each other then after the superposition the intensity is redistributed and this phenomenon is known as interference.

Coherent sources-

The sources of light for which waves produced by them do not have any change in the phase with respect to the time and those sources are known as coherent sources.

Note- Two independent light source can never be coherent sources because the light is emitted by individual atoms and when they a return to a ground state from the higher energy level and priority of returning billions of atoms at the same time at the ground state is negligible this is the reason why individual light source can never be coherent sources. Coherent sources of light can be obtained by the two methods one is a division of wavefront and another one is a division of amplitude.

Superposition of lightwave-

Consider there are two light waves and both the light waves are superimposed on each other while traveling in the same direction then the resultant waves are found by the principle of superimposition. As bright fringes lie between two constructive dark fringes. Soap for dark fringes the interference will be destructive interference.


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