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प्रश्न
There are two knitting needles. One of them is magnetized. How will you find out which one is magnetized, if no other magnet is available?
उत्तर
When an iron bar is magnetized, it slightly increases in length due to the setting of molecular magnets along straight chains. So, on precisely measuring the length of the knitting needle, the knitting needle which is slightly longer in length than the other is magnetized.
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संबंधित प्रश्न
Fill in the blank
To light a table lamp and to run a refrigerator, we use ______ as the source of electricity.
Tick the most appropriate answer.
The surest test of magnetism is
State if the following statement is true or false. Correct the statement if it is false.
Attraction is the surest test for magnetism.
If a magnet attracts a piece of metal, that piece must be made of ______.
Fill the blank spaces in the table given below:
| Nature of bar | Action of compass needle | |
| North Pole | South Pole | |
| Non-magnetic | No action | ________ |
| ________ | attracted | attracted |
| North pole of a bar magnet | ________ | _________ |
| ________ | attracted | repelled |
Give scientific reason:
Soft iron is used to make electromagnets.
The south pole of a bar magnet and the north pole of a U-shaped magnet will _______.
The magnetic poles always exist in pairs.
