In Class

1. A magnetic material will contain cobalt. True/False

Ans: true

2. Things made of aluminium material are non-magnetic. True/False

Ans: true

3. A freely suspended bar magnet will rest in the North-South direction. True/False

Ans: true

4. The North seeking end of a magnet is also called the North Pole. True/False

Ans: true

5. Every magnet has two poles. True/False

Ans: true

6. Unlike poles repel each other. True/False

Ans: false

7. The magnetic force exerted by a magnet varies with distance. True/False

Ans: true

8. Magnetic force is same all over the magnet. True/False

Ans: false

EXERCISE

I. Tick (✓) the correct option.

1. Which of the following metal is magnetic?

sliver/ aluminium/ iron/ gold

Ans: iron

2. What happens when a bar magnet is suspended freely?

it will always remain in the north south direction/ it will always remain vertical/ it will always remain in the East west direction/ it will start oscillating

Ans: it will always remain in the north south direction

3. Where is the magnetic strength of a magnet concentrated?

at North pole/ in the middle/ at the south pole/ at both the poles

Ans: at both the poles

4. Which of these materials can be used to make a temporary magnet?

a piece of iron/ a piece of paper/ a piece of wood/ a piece of plastic

Ans: a piece of iron

5. Which of these actions will result in the loss of magnetism of a magnet?

hammering/ washing/ sun-drying/ cooling

Ans: hammering

6. In which of the following devices magnets are used?

beam balance/ torch/ pendulum/ ATM card

Ans: ATM card

II. Tick(✓) the true statements and cross (×) the false the ones.

1. Magnets attract all metals.

Ans: ×

2. A freely suspended bar magnet remains in east west direction.

Ans: ×

3. The poles of a magnet can be separated.

Ans: ×

4. A magnet can attract/repel from a distance.

Ans: ✓

5. Non magnetic materials allow magnetic force to pass through it.

Ans: ✓

6. Magnets can never lose their property of magnetism.

Ans: ×

III. Answer the following questions in one sentence.

1. Name the natural magnet found in rocks.

Ans: Magnetite is a natural magnet found in the form of a rock in the Earth.

2. Name two magnetic materials.

Ans: Two magnetic materials:- iron and nickel.

3. Name two non-magnetic materials.

Ans: Two non-magnetic materials:- wood and plastic.

4. What happens if the like poles of two magnets are brought close to each other.

Ans: If the like poles of two magnets are brought close to each other than they will repel each other.

5. Where will you find the maximum magnetic force in a magnet.

Ans: The maximum magnetic force in a magnet is found in the poles.

IV. Answer the following questions in two sentences.

1. Distinguish between magnetic and non-magnetic materials giving examples.

Ans: Magnetic materials: 

          1. The magnetic materials are attracted by magnets.

          2. The magnetic materials are made of either iron or nickel or cobalt.

          3. Example: iron nails, iron fillings.

         Non-magnetic materials:

          1. The non-magnetic materials are not attracted by magnets.

          2. The non-magnetic materials are made of any other elements except iron, nickel and cobalt.

          3. Example: eraser, plastic bottles, bricks.

2. What property of a magnet is used to make a compass?

Ans: A freely suspended magnet always remains in the North-South direction. This property is used to make compass.

3. What will happen if a bar magnet is cut into four pieces?

Ans: If a bar magnet is cut into four pieces then each becomes a parmanent magnet.

4. How should two magnets be stored to avoid losing their magnetism?

Ans: To avoid magnetism the magnets must be kept with their opposite poles beside each other and magnets should not be taken near heat.

5. How is a compass helpful to sailors?

Ans: Since a magnet points in a North-South direction, it helps the sailors to find ways in the middle of oceans and seas.

6. What happens when a parmanent magnet is kept in contact with an iron nail for many days?

Ans: When a permanent magnet is kept in contact with an iron nail for many days, the iron nail becomes a temporary magnet.

V. Answer in about four to five sentences.

1. Explain with an experiment that a magnet attracts a magnetic object without being in contact with it.

Ans: A magnet can attracts a magnetic object without being in contact with it. It can be proved by the following experiment.

        Suppose a magnet is kept inside a plastic or paper coffee cup. When a magnetic object like iron nail is brought near the bottom of the cup then iron nail is attracted by the magnet though it is not directly in contact with the nail. 

2. List three ways by which a magnet can lose its magnetic strength.

Ans: The three ways by which a magnet can loose its magnetic strength are:

      a) if a magnet is taken near the fire.

      b) if a magnet is hammered.

      c) if a magnet is kept with like poles beside each other.

3. List any three uses of magnets.

Ans: The three uses of magnet are: 

       a) it is used to make compass.

       b) it used in toys, telephones, door bells, headphones, televisions, digital cameras, computers and refrigerators.

       c) to store information in a magnetic strip in credit cards and ATM cards

4. Describe how a piece of iron can be temporarily magnetised.

Ans: If a magnet is stroked on a piece of iron only in one direction, then the iron piece becomes magnetised.