Magnetic field around electric current carrying conductor Jonathan Koh Chen Si Hao 4S2.
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Transcript of Magnetic field around electric current carrying conductor Jonathan Koh Chen Si Hao 4S2.
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Magnetic field around electric current carrying conductorJonathan KohChen Si Hao4S2
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A bit on historyIn 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
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Electric current through a conductorA magnetic field is produced when a
current flows through a conductorDifferent 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
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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
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Experiment set-up
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ObservationsWhen 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
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ObservationsMagnetic field strength is larger when
larger current flows through the circuitWhen 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?
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Right hand grip rule (RHGR)
Current flows from positive end of battery to the negative end
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Magnetic field patternFlat coil
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Flat CoilWhat 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
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Magnetic field patternSolenoid
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AppletApplet
◦http://micro.magnet.fsu.edu/electromag/java/compass/
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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)
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Solenoid
Increase magnetic field by:1. Increase current2. Increase number of turns per unit
length3. Placing a soft iron core within
the solenoid
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Solenoid
Theory of magnetismIf 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
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Magnetic domainsEverything is made up of atoms
with electrons around the nucleusOrbiting 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.
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Magnetic domains
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Appletshttp://www.walter-fendt.de/ph14e
/mfwire.htm
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Thank you