Electric Motor
اسلاید 1: Electric MotorBy Princess BarcegaAPG SchoolPowerpoint hosted on www.worldofteaching.comPlease visit for 100’s more free powerpoints
اسلاید 2: Magnetic Force On A Current – Carrying Conductor The magnetic force (F) the conductor experiences is equal to the product of its length (L) within the field, the current I in the conductor, the external magnetic field B and the sine of the angle between the conductor and the magnetic field. In short F= BIL (sin)
اسلاید 3: The force on a current-carrying conductor in a magnetic field: When a current-carrying conductor is placed in a magnetic field, there is an interaction between the magnetic field produced by the current and the permanent field, which leads to a force being experienced by the conductor:
اسلاید 4: The magnitude of the force on the conductor depends on the magnitude of the current which it carries. The force is a maximum when the current flows perpendicular to the field (as shown in diagram A on the left below), and it is zero when it flows parallel to the field (as in diagram B, on the right):
اسلاید 5: Fleming’s left-hand rule
اسلاید 6: The directional relationship of I in the conductor, the external magnetic field and the force the conductor experiencesIFB
اسلاید 7: Motion of a current-carrying loop in a magnetic fieldNSLRIFFRotationCommutator (rotates with coil)brushes
اسلاید 8: Vertical position of the loop:NSRotation
اسلاید 9: Electric MotorAn electromagnet is the basis of an electric motor An electric motor is all about magnets and magnetism: A motor uses magnets to create motion. Opposites attract and likes repel. Inside an electric motor, these attracting and repelling forces create rotational motion. A motor is consist of two magnets.
اسلاید 10: Parts of the MotorArmature or rotor Commutator Brushes Axle Field magnet DC power supply of some sort
اسلاید 11: Motor Illustration
اسلاید 12: ArmatureThe armature is an electromagnet made by coiling thin wire around two or more poles of a metal core. The armature has an axle, and the commutator is attached to the axle. When you run electricity into this electromagnet, it creates a magnetic field in the armature that attracts and repels the magnets in the stator. So the armature spins through 180 degrees.To keep it spinning, you have to change the poles of the electromagnet.
اسلاید 13: Commutator and BrushesCommutator is simply a pair of plates attached to the axle. These plates provide the two connections for the coil of the electromagnet. Commutator and brushes work together to let current flow to the electromagnet, and also to flip the direction that the electrons are flowing at just the right moment.
اسلاید 14: The contacts of the commutator are attached to the axle of the electromagnet, so they spin with the magnet. The brushes are just two pieces of springy metal or carbon that make contact with the contacts of the commutator.
اسلاید 15: Spinning Armature
اسلاید 16: Example of Motor
اسلاید 17: Answer the questions
اسلاید 18: A current-carrying coil in a magnetic field experiences a turning effect.How can the turning effect be increased?A increase the number of turns on the coilB reduce the size of the currentC reverse the direction of the magnetic fieldD use thinner wire for the coil
اسلاید 19: What are the directions of the force in the left and right loop?
اسلاید 20: A student sets up the apparatus shown in order to make a relay.Which metal should be used to make the core? A aluminium B copperC iron D steel
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