Physics la a7la banat

• Electromagnetic induction


  The process of generating electrical current in a loop, caused by the relative movement between the wire and the magnetic field, that is, when the wire moves through the magnetic field or when the magnetic field moves through the wire
• Faraday Experiment


  Faraday put a part of a closed-loop wire within a magnetic field as shown in the figure, and studied the effect of wire movement in different directions on the generation of an inductive current in the electrical circuit
• Ways to obtain an induced current

  • The relative movement of the conductor or magnet so that it cuts the lines of the magnetic field
  • Change in the magnetic flux that penetrates the coil
• When the wire is moved vertically or oblique along the magnetic field lines, the galvanometer indicator deflects which indicates to the flow of current
• The current generation continues with the movement of the wire
• Electromotive force (EMF)


  The strength of the magnetic field times the length of the wire times the component of the velocity of the wire in the field that is perpendicular to the field
• RMS voltage


  Effective AC voltage
• Maximum voltage


  The highest voltage across a lamp connected to the outlet
• If the RMS current through the lamp is 5.5 A, what is the maximum current in the lamp
• Peak voltage


  The maximum voltage of an AC generator
• Veff


  The effective voltage in a circuit placed across the generator
• Lenz's law


  The magnetic field produced by the induced current is in the direction that is opposite the original field
• Determining induced current and magnetic field direction

  Using Lenz's law
• Eddy currents are generated in any piece of metal moving through a magnetic field
• Self-inductance


  The property of a wire either straight or in a coil to create an induced EMF that opposes the change in the potential difference across the wire
• Transformer


  A device that increases or decreases potential difference with relatively little waste of energy
• Only alternating current can be sent through a transformer. Direct current cannot pass through a transformer
• Principle of transformer work


  Depends on mutual inductance where an EMF and current in one coil due to changing current in another coil
• Components of transformers


  • Primary coil (P)
  • Secondary coil (S)
• The efficiency of the real transformer is between 95-98% which is the ratio of the output power to the input power
• Step-up transformer


  If the number of turns of the secondary winding is greater than the number of turns of the primary winding (Ns > Np)
• Step-down transformer


  If the number of turns of the secondary winding is less than the number of turns of the primary winding (Ns < Np)
• Dimensional analysis for EMF calculation

  • (N/A·m)(m)(m/s)
• Things generated when a piece of metal moves through a magnetic field


  • Eddy currents
  • Lenz's law
  • Voltage drops
  • EMF
• Transformer primary coil vs secondary coil turns

  Primary coil has twice as many turns as secondary coil
• What an electric generator converts

  Mechanical energy into electrical energy
• Lenz's Law states that the polarity of the induced emf opposes any change causing its production.
• Faraday's law states that the emf generated in an inductor depends on the rate at which the magnetic flux through it changes, with one volt being produced when the flux changes by one weber per second.
• When a conductor cuts across the lines of force, an EMF is produced in the conductor due to electromagnetic induction.
• A transformer consists of two or more coils of wire wrapped around a common iron core, allowing electromagnetic induction to occur between them.
• When the primary coil is connected across a battery, a potential difference (PD) is applied across the ends of the coil, creating a magnetic field within the core.
• The direction of the induced current can be determined using Lenz's law, where the direction of the induced current will oppose the motion or change producing it.
• The direction of the induced current is such that it produces a magnetic field which opposes the original change producing the current.
• The direction of the induced emf is given by Lenz's law, where the polarity of the induced emf opposes any change causing its production.
• A transformer consists of two coils wound around a common iron core, with the primary coil connected to an AC supply and the secondary coil used to produce a lower voltage output.
• The number of loops in the primary coil determines how much current flows through it, while the number of loops in the secondary coil determines how much voltage is produced.
• Alternating Current (AC): The flow of electric charge alternates periodically in one direction then reverses direction.
• Faraday's Law states that the electromotive force (emf) generated across a circuit loop due to a changing magnetic flux linking the loop is equal to the rate of change of the magnetic flux linked with the loop.
• • Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction.
  •  Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.
• Transformers use electromagnetic induction to transfer energy from one circuit to another without physical contact between them.