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When a coil or a conductor carries a current, it produces the magnetic flux around it.Then it starts behaving as a magnet. Such a current carrying coil or conductor is called an electromagnet. This is due to magnetic effect of an electric current. If such a coil is wound around a piece of magnetic material like iron or steel and carries current then piece of material around which the coil is wound, starts behaving as a magnet, which is called an electromagnet. The flux produced and the flux density can be controlled by controlling the magnitude the current, the direction and shape of the magnetic field around the coil or conductor depends on the direction of current and shape of the conductor through which it is passing. The magnetic field produced can be experienced with the help of iron fillings or compass needle. Let us study two different types of electromagnets, 1) Electromagnet due to straight current carrying conductor 2) Electromagnet due to circular current carrying coil Magnetic Field due to Straight Conductor When a straight conductor carries a current, it produces a magnetic field all along its length. The lines of force are in the form of concentric circles in the planes right angles to the conductor. This can be demonstrated by a small experiment. Consider a straight conductor carrying a current, passing through a sheet of cardboard. Sprinkle iron fillings on the cardboard. Small tapping on the cardboard causes the iron filling to set them in the concentric circular pattern. The direction of the magnetic flux can be determined by placing compass needle near the conductor. This direction depends on the direction of the current passing through the conductor. When current is going into the plane of the paper, i.e. away from observer, it is represented by a 'cross', inside the circle indicating the conductors. The current flowing towards the observer i.e. coming out of the plane of the paper is represented by a 'dot' inside the circle. Magnetic Field due to Circular Conductor: A solenoid is an arrangement in which long conductor is wound with number of turns close together to form a coil. The axial length of conductor is much more than the diameter of turns. The part or element around which the conductor is wound is called as core of the solenoid. Core may be air or may be some magnetic material. When such conductor is excited by the supply so that it carries a current then it produces a magnetic field which acts through the coil along its axis and also around the solenoid. Instead of using a straight core to wound the conductor, a circular core also can be used to wound the conductor. In such case the resulting solenoid is called Toroid. Use of magnetic material for the core produces strong magnet. This is because current carrying conductor produces its own flux. In addition to this, the core behaves like a magnet due to magnetic induction, producing its own flux. The direction of two fluxes is same due to which resultant magnetic field becomes stronger. Electrical Engineering Homework Help
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