PHYSICS LESSON

​LLET'S LEARN ABOUT

​A steelbar is placed inside a solenoid through which a direct current is passed for a while. A strong magnetic field is produced and the steel bar is magnetised.

When viewed at the end of the bar, the current flows in clockwise direction, that end becomes South pole. If the current flows in anticlockwise direction, it besomes a North pole.

​A magnet to be demagnetised is placed inside a solenoid. The solenoid is connected to an a.c. suppy. The magnet is withdrawn far away through the solenoid in the east-west direction while a.c. current is still flowing. As this process is repeated, the magnet will be demagnetised.

There are two ways to observe the magnetic field of bar magnet: 1) Plotting compass

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​To plot the magnetic field of a bar magnet, a small plotting compass is placed near one end of the magnet. (Position X). The compass needle are marked with dots 1 and 2. The compass is then shifted to position Y with the South pole of the needle pointing dot 2. The position of dot 3 is marked.

​This process is repeated until the compass reaches the other end of the magnet. All the dots are joined to obtain the MAGNEIC FIELD LINES or MAGNETIC LINES OF FORCE.

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There are two ways to observe the magnetic field of bar magnet: 2) Iron Filings