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Magnetic field around electric current carrying conductor

Magnetic field around electric current carrying conductor. Jonathan Koh Chen Si Hao 4S2. A bit on history. In 1819, Hans Christian Oersted , a professor at the University of Copenhagen, accidentally discovered the magnetic effect of an electric current

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Magnetic field around electric current carrying conductor

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  1. Magnetic field around electric current carrying conductor Jonathan Koh Chen Si Hao 4S2

  2. A bit on history • In 1819, Hans Christian Oersted, a professor at the University of Copenhagen, accidentally discovered the magnetic effect of an electric current • While demonstrating the heating effect of current to his students, he noticed that a compass needle nearby was deflected when the current was switched on. • Led to discovery of electromagnetism

  3. Electric current through a conductor • A magnetic field is produced when a current flows through a conductor • Different magnetic field patterns are set up due to different dimensions of the conductor • Direction of the magnetic field is based on the direction of the current in the circuit

  4. Experiment (Magnetic field pattern for straight wire) • Place a wire upward through a small hole in a horizontal cardboard • A fine layer of iron filings is then sprinkled on the cardboard • The current is switched on and the card tapped gently • The filings set in a series of concentric circles about the wire as the centre

  5. Experiment set-up

  6. Observations • When iron filings are sprinkled around a conducting wire, the iron filings are pulled to form concentric circles around the wire • The distance in between the circles increases at an increasing rate – Magnetic fields strength is stronger nearer the wire

  7. Observations • Magnetic field strength is larger when larger current flows through the circuit • When direction of current is reversed, the north pointer of the compass switches to the position of the south pointer • Concentric circles of iron fillings remains • So how to find direction of magnetic field?

  8. Right hand grip rule (RHGR) • Current flows from positive end of battery to the negative end

  9. Magnetic field pattern • Flat coil

  10. Flat Coil • What happens at the centre of the coil? • The fields due to the sides of the coils are in the same direction and they combine to give a strong magnetic field

  11. Magnetic field pattern • Solenoid

  12. Applet • Applet • http://micro.magnet.fsu.edu/electromag/java/compass/

  13. Solenoid • Increases the number of turns of a flat coil makes it a solenoid • Magnetic field pattern resembles that of a bar magnet • The end that current is flowing towards through the solenoid is the N pole (RHGR)

  14. Solenoid • Increase magnetic field by: • Increase current • Increase number of turns per unit length • Placing a soft iron core within the solenoid

  15. Solenoid • Theory of magnetism • If we take a bar magnet and cut it into two pieces, each piece becomes a magnet itself with a N pole and a S pole

  16. Magnetic domains • Everything is made up of atoms with electrons around the nucleus • Orbiting motion of electrons in sets up a magnetic dipole causing each atom to become a atomic magnet • A group of atomic magnets pointing in the same direction is called a magnetic domain.

  17. Magnetic domains

  18. Applets • http://www.walter-fendt.de/ph14e/mfwire.htm

  19. Thank you

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