v) How can we magnetize a steel bar by stroke method?
Answers
Stroking Method
Procedure:
The steel bar is stroked with the same pole of the permanent magnet from one end to the other end in one direction.
The stroking magnet has to be lifted sufficiently high above the steel bar between successive strokes.
The steel bar will become a magnet with pole produced at the end where the strokes finish is opposite to the stroking pole used as the atomic magnets in the domain are attracted to the stroking pole.
Note:
When using two magnets, the stroking pole used in each magnet has to be opposite, and they stroke the steel bar in opposite direction.
Using two magnets to stoke is faster than that using one magnet.
Stroking method only produces weak magnets.
Explanation:
Find a strong magnet. (you can use any magnet to “pass on” the magnetism to the steel, but ordinary refrigerator magnets will have a very weak effect)
Test the steel’s reaction to the magnet. If the steel doesn’t respond to the magnet, it can’t be turned into a magnet itself.
Stroke the magnet along half the steel, repeatedly. Hold the steel object in one hand. Stick the magnet to the steel about halfway along its length, then drag it to one tip. (repeat several times, stroking only in one direction, and only along half of the steel. The more you do this, the more magnetized the steel will become)
Stroke the opposite end of the magnet along the other half. Flip the magnet over so the other pole touches the steel. Place it against the steel at the midpoint again, but drag it the other way, toward the end of the steel that wasn’t rubbed earlier. Repeat until the steel can pick up a paper clip, or continue to rub to increase the strength slightly.
This method is ideal for magnetizing a screwdriver, nail, or needle just before use. You can also use it to restore magnetism to an old compass needle or other weakened magnet. Also note that this method is easiest to use on long, thin pieces of steel, such as screwdrivers or nails, but will work on any shape of steel.