Physics Report Sem 3 Ppismp

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  • Topic: Magnetic field, Earth's magnetic field, Magnet
  • Pages : 5 (1299 words )
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  • Published : February 17, 2011
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Group member’s name: Annie Wong Ai Yuan
Huong Sing Yi
Kee Guan Yang
Teh Boon Chuan
Tham Hua Yuan

Experiment 9
Magnetics field
To study the behavior of a bar magnet in varying magnetic fields at the end of a solenoid and hence estimate the horizontal component BH of the Earth’s magnetic fields. Theory
A magnet is an object that can exert a magnetic force to any object around it. When a ferrous object is placed near it, the magnetic force will attract it towards the magnet. The magnetic force forms a magnetic field around the magnet which is invisible to human naked eye. When two magnetic fields from two different magnets meet, attraction or repulsion will occur between the magnets according to the pole of the magnetic fields. [pic]

From the diagram, we can see that the magnetic field has a direction. The magnetic force come out from the N pole and goes to the S pole. There are no distinguished lines which separate the N and S pole in a magnet. One part of the magnet will always be N and the other will always be S.

When hanged freely in the air, a bar magnet will always pointed to a fixed direction even with the absence of other magnet in the surrounding. This is because our earth behaves like a magnet and has a magnetic field of its own. This also means the magnetic field of the earth has a N and S pole as well. [pic]

Since a magnetic field always start from the pole and head toward the S pole, the magnetic field of the earth will affect a freely hanged bar magnet and cause it to point to a fixed position. The N pole of a magnet will always point to the S pole of the earth if there are no any other forces involve. The continuous production of magnetic field from the earth can be explained with the Dynamo Theory. When conducting fluid flows across an existing magnetic field, electric currents are induced, which in turn creates another magnetic field. When this magnetic field reinforces the original magnetic field, a dynamo is created that sustains itself.

Magnetic field can be produced artificially. When current flow through a wire, a magnetic field is produce around the wire. The direction of the magnetic field is depending on the direction of the current. But this kind of magnetic field is not permanent. As soon as the current is turn off, the magnetic field disappear. [pic] [pic]

When the wire is loop into a circle, the magnetic field of all parts of the looped wire combined and forms a magnetic field similar to a bar magnet. The magnetic field will come out from a side and head to the opposite side just like the N and S pole of a magnet. When the turn of wire is increased, a solenoid is formed. [pic]

The solenoid can be treated as an artificial bar magnet. The N and S pole of the solenoid is depending on the direction of the current flowing through the solenoid. The strength of the magnetic field produce depends on the number of turns in the solenoid and the voltage of current applied. In this case, we can easily manipulate the strength of magnetic produced by adjusting the voltage of the current. Apparatus

i) A retort stand and two clamps
ii) A cork and an optical pin
iii) A set of small bar magnet fixed with a pair of optical pins iv) A plane mirror attached to a protractor
v) Thread of length about 40cm
vi) A test tube wound with copper wires
vii) A 2V accumulator or any other stable power supply
viii) A (0-1) dc ammeter
ix) An on-off switch and three connecting wires
x) A rheostat
xi) A pair of vernier calipers
xii) A micrometer screw gauge

1) The cork is clamped with a pin to a retort stand and the bar magnet is hanged from the pin using the thread. 2) The magnet is fixed at a position where...
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