Science : Term 3 Unit 1 : Magnetism
I. Choose the correct answer:
1. An object that is attracted by magnet.
- wooden piece
- plain pins
- a piece of pape
Ans : plain pins
2. People who made mariner’s compass for the first time.
Ans : Chinese
3. A freely suspended magnet always comes to rest in the _____________ direction.
- North – east
- South – west
- East – west
- North – south
Ans : North – south
4. Magnets lose their properties when they are
- hit with a hammer
Ans : hit with a hammer
5. Mariner’s compass is used to fi nd the
Ans : direction
II. Fill in the Blanks
1. Artificial magnets are made in different shapes such as __________, __________ and ____________.
Ans : bar magnet, horse shoe magnet, ring magnet
2. The Materials which are attracted towards the magnet are called________.
Ans : magnetic materials
3. Paper is not a ______ material
Ans : magnetic
4. In olden days, sailors used to find direction by suspending a piece of ___________.
Ans : bar magnet
5. A magnet always has __________ poles.
Ans : two
III. True or False. If False, give the correct statement
1. A cylindrical magnet has only one pole.
Ans : False
Cu. An. : A cylindrical magnet has two pole.
2. Similar poles of a magnet repel each other.
Ans : True
3. Maximum iron filings stick in the middle of a bar magnet when it is brought near them.
Ans : False
Cu. An. : Minimum iron filings stick in the middle of a bar magnet when it is brought near them.
4. A compass can be used to find East-West direction at any place.
Ans : True
5. Rubber is a magnetic material
Ans : False
Cu. An. : Rubber is a non-magnetic material.
IV. Match the Following
|1. Compass||Maximum magnetic strength|
|2. Attraction||Like poles|
|3. Repulsion||Opposite poles|
|4. Magnetic poles||Magnetic needle|
Ans : 1 – D, 2 – C, 3 – B, 4 – A
V. Circle the odd ones and give reasons
1. Iron nail, pins, rubber tube, needle
Ans : rubber tube
Reason : It is a non magnetic material.
2. Lift, escalator, electromagnetic train, electric bulb.
Ans : electric bulb
Reason : It is run help of electricity only.
3. Attraction, repulsion, pointing direction, illumination.
Ans : illumination
Reason : the action of illuminating or decorative lighting.
VI. The following diagrams show two magnets near one another. Use the words, ‘Attract, Repel, Turn around’ to describe what happens in each case.
Ans : a & c
Ans : b & e
Ans : d & f
VII. Write down the names of substances.
Substances attracted by magnets → Nail,Iron rod,Hairpin,Nickel,,Cobalt, Rare earth metals, dysprosium metal.
Substances not attracted by magnets → Plastic,Wood,Rubber,Silver,Copper, Paper,Gold
VIII. Give short answer
1. Explain the attraction and repulsion between magnetic poles.
Unlike poles (S-N, N-S) attract each other. Like Poles (N-N, S-S) repel each other.
2. A student who checked some magnets in the school laboratory found out that their magnetic force is worn out. Give three reasons for that?
The magnetic force is a consequence of the electromagnetic force, one of the four fundamental forces of nature, and is caused by the motion of charges. Two objects containing charge with the same direction of motion have a magnetic attraction force between them. Similarly, objects with charge moving in opposite directions have a repulsive force between them.
IX. Answer in detail
1. You are provided with an iron needle. How will you magnetize it?
Take a iron needle and place it on a table. Now take a bar magnet and place one of its poles near one edge of the iron needle and rub from one end to another end without changing the direction of the pole of the magnet. Repeat the process for 30 to 40 times.
Bring a pin or some iron filings near the iron needle to check whether it has become a magnet. If not, continue the same process for some more time.iron needle become a magnet.
2. How does the electromagnetic train work?
Electromagnets are used in Electromagnetic train. Electromagnets are magnetised only when current flows through them. When the direction of current is changed the poles of the electromagnets are also changed. Like poles of the magnets which are attached at the bottom of the train and rail track repel each other. So, the train is lifted from the track up to a height of 10 cm.
We Know that we can move any magnetic object with the force of attraction or repulsion properties of magnets. This train also moves with the help of the magnets attached on the sides of track and the magnets fitted at the bottom sideway of the train. By controlling the current we can control the magnets and movement of the train.
As there are no moving parts, there is no friction. So, the train can easily attain a speed of 300 km per hour. These trains are capable of running up to 600 km/ hour. They do not make any noise. They require less energy and they are eco-friendly.
Even though, many countries have taken effort to use these trains, such trains are used for public transport only in China, Japan and South Korea. In India the possibilities of introducing these trains are under consideration