Electricity and Magnetism

Summary/Synthesis/Feedback

  • Many of the audio-video recording technology apply the relationship between electricity and known as electromagnetic induction.
  • A typical recording studio consists of an audio-video console, microphones, computers, studio monitors or speakers, disc players and cables used for the exchange of audio and digital data signal during production, recording. mixing, and even editing of all audio-video elements digitally stored on disk drives.
  • Devices that detect and convert audio inputs to electric outputs or vice versa are called transducers. Most transducers like microphones and speakers use the "generator effect" characterized by the production of electromotive forces due to either a changing electric signal within a magnetic field or a changing magnetic field near a current-carrying conductor.
  • Magnetism is commonly attributed to ferromagnetism and electromagnetism on the material and moving charges. Every atom and all moving charges are in constant motion and therefore has a bit of magnetism due to magnetic coins and domains creating a net magnetic field.
  • A magnet has two magnetic poles (north and south seeking poles).
  • Stroking with a permanent magnet is one of the ways to induce or cause magnetism in an object that can be magnetized. The polarity of the induced magnetism in the object is opposite to the polarity of the nearer end of the permanent magnet. Attraction happens after magnetic induction occurs.
  • A magnet attracts, but do not repel, unmagnetized ferromagnetic materials such as iron, nickel, cobalt and some of its alloys like steel and alnico.
  • Both forces of attraction and repulsion is possible between magnets and between a magnet and a temporarily magnetized object.
  • A magnetic field surrounds a magnet. Within this region, the magnet affects another magnet and other objects that can be magnetized.
  • The magnetic field is strongest at the poles where the magnetic lines of induction (flux) are closest. The magnetic field pattern can be shown using iron filings that align along magnetic lines of induction
  • The magnetic lines of induction leave the north-pole and enter the south-pole in close loops and can be indicated by the north pole of a compass.
  • The magnetic field increases in direct proportion to the number of turns in a coil with the compass needle, at the center of the coil of wire, deflecting about a wider angle than the compass needle along the straightened wire.
  • The end of the current-carrying coil where the magnetic lines of induction come out acts as the north pole of the coil.
  • A magnetic field exerts a force on a current-carrying conductor. Using the right-hand rule, the direction of this force is in the direction where the palm faces.
  • The motor effect is shown when a current-carrying conductor within a magnetic field moves in the direction of the force. The force on a moving current carrying conductor may be varied by changing the magnetic field.
  • An electric motor is a device that converts electrical energy into rotational mechanical energy. A simple DC motor can be assembled using a single coil that rotates in a magnetic field. The direct current in the coil is supplied via two brushes. The forces exerted on the current-carrying wire creates a rotation-causing force on the coil.
  • An electric generator is a device that converts mechanical energy into electrical energy. A simple electric generator is made when a coil cr any closed loop of conductor moves through or cuts across magnetic field lines. The coll will experience an induced voltage or an electromotive force that will cause a pulsating direct current (DC) to be generated. The pulsating direct current fluctuates in value but does not change direction.
  • Electromagnetic induction is a process in which electric current is generated in a conductor by a moving or changing magnetic field.
  • A changing magnetic field occurs when there is relative motion between a source of a magnetic field and a conductor; it does not matter which moves.
  • A changing magnetic field may also arise from a changing nearby current.
  • The amount of voltage (EMF) induced when a conductor and a magnetic field are in relative motion depends on (a) the length L of the conductor or the number of turns in the coil, (b) the strength and orientation of the magnetic field B relative to the conductor, and (c) The relative velocity v of the changing magnetic field.