Class Notes NCERT Solutions for CBSE Students
Question: Before invention of compass, sailors used stars to find directions. In what way is using a compass better?
Answer: Using a compass is better as stars are only visible at night and sometimes they are not seen at night due to pollution and clouds and stars change their position every night.
Question: Give a bar magnet, how will you find west direction?
Answer: To find west direction with a bar magnet we will tied the magnet and leave it freely as a freely suspended magnet alligns itself in north-south directions. As it is free and it is tied using a copper wire stirrup. slowly it will itself move towards North and we can locate the west.
Question: A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole located?
Answer: Take the bar magnet and suspend it freely with the help of a thread, the end that points towards north pole will be regarded as north end of the magnet. Take a bar magnet with known / marked poles on it. Let the north pole of the magnet be brought closer to the suspended magnet at the end that is pointing towards north, if it shows repulsion than it is confirmed.
Question: You are given iron strip. How will you make it into a magnet?
Answer: Making a magnet: Take an iron strip and place it on the table. Now take a bar magnet and place one of its poles near one edge of the strip of iron. Without lifting it move it along the length of the iron strip till you reach the other end. Now lift the magnet and bring the pole to the same point of strip from where yob began. Repeat this process about 30-40 times. Bring some iron fillings near the strip and observe that the strip attracts the fillings. This indicates that the iron strip becomes magnet.
Remember that the pole of magnet and direction of its movement should not change.
